The following cheats can be performed during a local match or replay only. You must simultaneously PRESS & HOLD the following buttons for 3 SECONDS to toggle the effect on / off.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Complete the indicated task in Campaign mode to unlock the corresponding armor part in Multi-player mode.

Complete the final mission under the Legendary difficulty setting.

Collect the hidden skulls throughout the game to unlock the pieces of Hayabusa armor.

Katana is unlocked when you complete all Achievements (1000/1000) and find all skulls..

A list of the Skill and Experience needed to advance in rank. Note: you can skip ranks once there is a set skill requirement. For example, many people go from Lieutenant Grade 2 (Skill:10 EXP:85) straight to Captain (Skill:20 EXP:100)

If you do the following things you will get the medal while playing multiplayer. When you do the task usually it will show you by a little icon of the said medal appearing in the corner of the screen. Also at the end of each match you can check what medals you got. You can also check your overall medal count on bungie's official website. A very small amount of these are secret medals in that they don't tell you right when you get them but they will appear in your medal history. (One example of such a medal is the Steaktacular! Medal)

To get katana armor you need to get 1000/1000 gamescore.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Recruit - 1 EXP

Apprentice - 2 EXP
Apprentice G2 - 3 EXP

Private - 4 EXP
Private G2 - 5 EXP

Corporal - 7 EXP
Corporal G2 - 10 EXP

Sergeant - 12 EXP
Sergeant G2 - 15 EXP
Sergeant G3 - 20 EXP

Gunnery SGT - 25 EXP
Gunnery SGT G2 - 30 EXP
Gunnery SGT G3 - 35 EXP
Master Gunnery SGT - 40 EXP

Lieutenant - 50 EXP
Lieutenant G2 - 60 EXP
Lieutenant G3 - 70 EXP
First Lieutenant - 80 EXP

Captain - 100 EXP
Captain G2 - 110 EXP
Captain G3 - 120 EXP
Staff Captain - 135 EXP

Major - 150 EXP
Major G2 - 160 EXP
Major G3 - 170 EXP
Field Major - 185 EXP

Commander - 200 EXP
Commander G2 - 225 EXP
Commander G3 - 250 EXP
Strike Commander - 275 EXP

Colonel - 300 EXP
Colonel G2 - 325 EXP
Colonel G3 - 350 EXP
Force Colonel - 375 EXP

Brigadier - 400 EXP
Brigadier G2 - 425 EXP
Brigadier G3 - 450 EXP
Brigadier General - 475 EXP

General - 500 EXP
General G2 - 1000 EXP
General G3 - 1500 EXP
5-Star General - 2000 EXP

Get all of the Vidmaster achievements, when the mythic map pack comes out.

You can only claim/collect the skulls under the Normal, Heroic or Legendary difficulty settings. You must start from the beginning of the mission. You will not be able to see the skulls if you load from a checkpoint. In Co-op mode, as soon as one player picks the skull up, all players will receive the achievement. Not all skulls earn an achievement; only nine of them do so. To use skulls, press X at the lobby screen. This will give you a bonus multiplier for co-op and go towards earning the Guerrilla, Demon, etc. achievements.

From the start of the "Crow's Nest" mission, without moving anything, you can see a massive pipe above you. Walk up the stairs, then up the next set. Turn to your left and jump up on the shelf unit. From there, jump to the red cross beam then up onto the pipe. From there, just walk to the end. Walk over the Black Eye Skull to claim it. You do not have to pick this skull up, it does it automatically. Its description reads "Bash your way to better health." Your shield will not auto-recharge anymore, and you must kill an enemy with a melee attack.

In the first mission, get to the area where you see the Phantom overhead. A Marine will point it out. Jump over the rocks and follow the path on the right. When you reach the cliff, there will be a rock over the side. The skull is at the end of the rock. Its description reads "Shoot from the hip". This skull must be activated before you start a Campaign map.

Immediately after the first objective of the "Crow's Nest" mission, while en route to the barracks you will fall down to a pipe. Get to the end that pipe. Look over the edge to find a small space a few feet below. Drop over then quickly pull back to land under the floor you dropped from. The skull will be at the end of this area. When this skull is active, headshots will cause enemies to explode.

After freeing Johnson and killing all the Covenant that come in the Phantoms in the "Sierra 117" mission, walk to the Pelican that arrives to pick you up. Face the cargo bay, but instead of hopping in turn left and follow the path. Once you hit the wall, jump up to your right to eventually reach a walkway. Walk all the way to the end. Take a left, then a right. At the end of this a little bit to the right is a dark corner. Press Up to turn your light on and you should see the skull. If you cannot see it you are probably standing on it. Its description reads "Death carries a heavy price...". Instead of only losing 25 points when you die, you will lose 75.

Follow the normal path in the "Halo" mission until you reach a cave. Hug the right wall until it branches off into a small path. At the end of this path is some rubble, and in front is the skull. Its description reads "Coverage under the Covenant health plan." It gives a 3x score multiplier for all kills.

Mission: Cortana - When in the circular type room with all the flood look for a small structure piece next to two archways, jump on top if it and up on the rocks to the top left, turn left and jump up again, then do a 180 and jump to the rocks across from you. After that follow the the rock sticking out and leading up on top of of the original circular room, the skull will be in a pile of blood.

On Tsavo Highway, about halfway through the mission (right after you are forced to walk through a large blue barrier), you will come out of a tunnel on the highway, and see a large pipeline on your left. Drop down in between the two, and run to the wall in front of you. Follow the wall all the way to where it connects with the cliff on your right, and turn to the left. There should be a few ledges--simply crouch jump from ledge to ledge, and the last one should have the "Tough Luck" skull on it

In "The Storm" mission, do a grenade jump off a Warthog; or get a Ghost and go back to the ramp from which you first appeared. Use the Ghost to push a big square crate over to the front of the silo pod that has the skull. Jump from the box to reach the skull. Its description reads "Pull pin. Count to three. Throw." All NPCs will have two grenades and will throw them frequently.

First pick up a grav lift from the small building near where you fight the scarab. Now proceed through the level until you reach the second sloping hallway (stairway), you should see some partitioned risers (platforms) halfway down. The skull is on the top level. Toss the grav-lift on the right side of the hall so it lands on the fourth little green dot from the door. Then run, jump, and use the grav-lift to propel you to the top. You should reach a ckeckpoint just as you enter the room so it you miss just try again.

In "The Ark" mission, enter the valley to the right after the wrecked Phantom. Look to the left to find a large boulder. Use a Ghost to reach the side of the boulder that is closest to the bridge overhead. Get the Ghost up the side of the wall by using the thrust. Get two Ghosts up the wall to the top of the bridge. Stack them on top of each other next to the beam where the skull is located. Then, jump from the top of the Ghosts towards the skull and land on the beam. Its description reads "Trust us. Bring a magazine." Dropped weapons will have less ammunition.

In the "Floodgate" mission, while you are walking down from the anti-air gun destroyed in the last mission, you will see a ramp next to a missile launcher. Near this ramp is a checkpoint. After reaching it, you will hear a Marine yell, "There! Over there!". Look up and to the right at the roof of the building next to the missile launcher. There is a lone Flood that is holding the skull. Kill him before he jumps. He will drop the skull on the ground. Note: If you shoot too early the skull will get stuck on the roof. Its description reads "You'll miss those eyes in the back of your head." You will no longer have a motion sensor.

In "The Covenant" mission, shut down Tower 1 and get access to the Hornet. Fly to Tower 2 (which is the one that the Arbiter shut down). Go up the stairs. Go to the middle part that connects both. There should be a stairway that leads up to a platform where the skull is found. Its description reads "Field promotions for everyone!" Enemies will be stronger.

When playing in Co-op under the Legendary difficulty setting, it is best to have one player keep their distance from the enemy at all times. By doing this, if the rest of the players die they will respawn around the player that is farther back, rather than having to restart the checkpoint.

After you come into contact with the snipers in the woods, follow along the left rock path. You will find a strange family of monkeys holding a teddy bear.

Go to the last tower. Before you get to the Prophet of Truth, there are a series of bridges with Halos. Do not jump through any yet. First, kill the Prophet and clear the bridges of enemies. Then jump through the Halos in this order, with "1" being the entrance and "7" being the end near where the Prophet was located: 4, 5, 6, 5, 7, 6, 5, 4, 1, 2, 3, 2, 7, 2, 1, 3, 4, 6, 7, 5, 4, 6, 5, 4, 5, 3. This is much easier in Co-op mode with three or four people. This is the Halo theme if it was played on a phone by dialing the numbers. If done properly, the Halos will start flashing. If the Halos do not flash, revert to your last saved game. The skull is near the Prophet's ramp. Its description reads "But a dog beat him over the fence." This skull unlocks hidden dialogue when activated. If this is the thirteenth skull you have located, it will also unlock the Hayabusa Head. IWHBYD stands for "I Would Have Been Your Daddy" which is a level chapter from the original Halo.

Start "The Ark" mission. After entering the first building take a left into another door. You will be in a curved corridor. On the inside is a Terminal.

After activating the bridge in "The Ark" mission to let your friends cross the gap, turn 180 degrees to find the Terminal. Note: It does not open until you activate the bridge/

In the third building after defeating the Scarab in "The Ark" mission, kill the group of sleeping Covenant. Follow the corridor down. You will reach a door in front that is locked. Immediately on the left is an open door. Go through and walk straight off. Turn 180 degrees to find a secret room with the Terminal.

Enter the first tower standing on the lift in "The Covenant" mission. Face the access panel and turn left. Jump over to find the Terminal.

Land your Hornet on the second tower in "The Covenant" mission. Walk towards the entrance. When you see the locked door, turn 180 degrees to find the Terminal.

When in the third tower standing on the lift in "The Covenant" mission, face the access panel then turn right. Jump over to find the Terminal.

After reaching the end of the first cave in the "Halo" mission, hug the right wall. You will see a building. Jump up onto the walkway and turn to the left once you are inside to find the Terminal.

This is best done with two players. Enter the Sandtrap on the Forge. Try to get as many pre-placed fusion coils and plasma batteries before you start. Place as many fusion coils and plasma batteries as possible in front of an Elephant and drive into the pile. Then, shoot into the pile until it explodes. It will either just jump a little, stand up on the rear, or turn all the way around. When you get close, the message "Press RT to... Wait. How did you do that?" will appear.

When you kill any Flood that can come back to life by the infection forms, hit the body and it should break apart. This saves ammunition.

On the multi-player map Isolation, go to the Flood cave where the Ghost is located. Go in front of the Ghost, look up, and walk a short distance slowly. You will see a big smudge on its face, but look carefully for the duck's body. You can partly see its face and the horns on its head. This is related to the picture in Zanzibar in Halo 2.

Go to your Dashboard. Change your language to the second option from the bottom. Start Halo 3. Invite four other friends that are about the same rank as you. Also have them change their language to the same one as you. Get everyone in the same party before you want to get them in the same party. Everyone must search at the same time. Everyone then must make a game in Lone Wolves. Before you go to start the countdown, press X to change the search options to the bottom one, which is to search for the same language. If done correctly, chances are you will be in the same ranked Lone Wolves game as your friends. You can now get achievements or level someone up.

At the beginning of the level, grab the skull on top of the large pipe near the ceiling before you pick up any weapons. This is easier in Co-op mode. Press RT repeatedly. This will cause Master Chief to drop the skull but because he has no weapons, he will immediately pick it back up, making it appear as though he is dribbling the skull like a basketball.

To easily destroy a Wraith and save time and ammunition, go to the back side. Aim at the little circle in the back. With about five to ten shots it will be destroyed.

Go to your Dashboard. Change your language to the second option from the bottom. Start Halo 3. Invite four other friends that are about the same rank as you. Also have them change their language to the same one as you. Get everyone in the same party before you want to get them in the same party. Everyone must search at the same time. Everyone then must make a game in Lone Wolves. Before you go to start the countdown, press X to change the search options to the bottom one, which is to search for the same language. If done correctly, chances are you will be in the same ranked Lone Wolves game as your friends. You can now get achievements or level someone up.

in multi-player or system link mode, when you kill someone slash their dead body with the Energy Sword. More grenades come out of it.

When playing in Co-op under the Legendary difficulty setting, it is best to have one player keep their distance from the enemy at all times. By doing this, if the rest of the players die they will respawn around the player that is farther back, rather than having to restart the checkpoint.

In Forge mode get a Spartan laser. Charge it until its almost about to fire. Before you fire, turn into the Monitor. Fly around until you get a target. Before you turn back into a human, hold RT to fire within at least half a second (if done correctly). You can use the Monitor's aimer to aim the laser.

In the level the storm, grab a sniper rifle as soon as possible to shoot enemies with, but conserve at least 16 rounds of amunition(full clip w/ 12 round remaining) then, when u get 2 the part where you have 2 charge the aa gun, hang back and scope ur sniper rifle. When the gun fires, the bottom will open up, revealing the crystal area u have 2 shoot 2 destroy the gun. If your fast, you can get 3 shots on it before it closes. keep doin this until it explodes

Note: Your aim will rise a bit above the crystal if u hit it.

You hold LT and RT and click X three times and there you go.

Press Up at the Forge lobby and you will turn into the Oracle. You can pick up items by pressing A when you see a green hand.

Note: The following can only be done in a local match or replay. To do the at ease position you must hold LB + RB for at least three seconds and press Left. If done correctly, your weapon will not be visible on your screen. When you shoot you will raise your weapon again.

If your shields are down in Forge mode, press Up and they will recharge.

If you are a Spartan or Elite and your ammunition is low and it takes a long time to reload, press Up again while reloading to instantly reload.

To melee faster, press B then press Y(2), B rapidly. It will hit again immediately.

When Battling Brute Flood, just jump over them when they attack then shoot them, repeatedly in the "chest".

Go through the level normally until you get to Voi (you just got out of your warthog and jumped across the broken road). Go through the little tunnel and turn right. You should see some rocks. Jump on top of them until you reach the top. Face the little shack, but don't go in. Turn right and go in front of it. Then turn left and there should be two dead grunts, a dead brute, and a dead marine on the ground. The sniper rifle is by the marine. Shoot carefully, you only get 12 shots. This is not recommended because once out of ammo with the sniper, it is hard to stay alive with the little weaponry you have.

If you're the only 1 playing, go to multiplayer, then sign in 2, and i repeat, 2 players (yours and someone elses). Then set kills to 25, and just start kiling them, then u get the points, and that secret medal.

If you make fusion coils and put street cones in front of the coils, and stand in front of them. If you at the right angle and you blow up the coils, a cone will fly at you and kill you. It says you have commited suicide.

Go to Forge, and if anyone sticks you with a plasma or spike grenade turn into the oracle(monitor). Then go up to them and turn back into you person and it will explode.

P.S. This works best with plasma

P.S.S. if you wait to long in monitor mode the grenade will not detonate when you go back to your character.You can hear the sound of the grenade.

If someone has a gravity hammer and someone else has a rocket launcher. Shoot the rocket at the person with the gravity hammer. If the person with the gravity hammer swings it(RT) at the right time it will deflect the rocket away from him or her.

It has been confirmed that to get the IWHBYD Skull you don't need ALL of those notes, all you need is 4654534. You HAVE to kill the flood and the Prophet of Truth before you do this. If you mess up just start with 4.1 is where you enter and 7 is at the bridge near where you kill the Prophet. It unlocks hidden dialog through out the game. You MUST complete the level with the skull to actually unlock it.

Blind Skull: You start out on Sierra 177 and you go along the path way until you come across a river.Then you will climb over some sort of log. You will se a series of grunts and a couple Brutes. Trail off to the right. You will come to a cliff but under you there is a ledge. On the very end there will be "the Blind skull"

You need to press more than RB and LB. You need to press RB, LB, DOWN(on D-PAD), A BUTTON and click the left analog stick all at once for about 3 to 5 seconds. May take a couple tries.

To play the halo meta-game and get the achievement is as follows:

In the lobby while waiting for the level to load press X. at the top of the pop up screen is text which asks you if you want to play the meta-game. Change to yes. Now activate all skulls exept for the first 2 gold and first silver. Nothing else is needed to get the achievement exept the reqiured score at the end of the level.

The brutes are now nearly impossible to kill as well as most covenant forces.you should always carry a battle rifle and a carbine to take care of jakels and grunts with head shots. The best way to take care of brutes is with a plasma or spike grenade. if you run out there should always be some on grunts so kill a couple and youll be fully stocked. Hunters are nearly impossible to kill so try to let the arbiter take care of them or just run away.

Note: the flood dont get any improvment so there missions should be easy.

Note: play on normal to get the achievment otherwise its too hard

Find the stairs with out the fences. All you have to do to get under them is walk forward while clicking the analog stick down repeatedly to walk underneath them. This would be best to do during an oddball game or if your winning and want to hide the rest of the game you wont be found, unless the opposing team knows how to do this also, but not very many people do.

To get the Catch Skull you must be on normal or higher and you must have completed the game on normal or higher.The skull is located in the first area of the level(Where the first anti air wraith is). IMPORTANT, YOU CAN'T KILL ANYTHING BUT THE GHOSTS!!!See the big cylinder at the other side of the area, you must either have two people playing jump on their head you jump then they jump then you jump again off there head(recomended). Or you must get on a Warthog behind the cylinder so the normal Wraith cannot kill you.

In Forge make any equiptment, trip mine the the best one to do it with. Delete all of that item, then place at least two in one place. Set respawn time for that item at 10 seconds. While you on this menu to do respawn time, hit X again. Then set the minimum setting as what the maximum is.

Stand on the pile and just keep hitting X to keep throwing whatever it is you did this with bubble shield, trip mine,power drain, etc.

Pause and go to settings. Turn the horizontal turn to the highest it can go to.
Pick up a machine gun or any other fast shooting gun. Keep holding left on the right contol stick and keep spining and hold the fire button. Super speed! this is helpful if you need to take out a bunch of grunts. Tip: how about picking up TWO machine guns? this shall increase damage! GO ON A RAMPAGE!!!!!!

In Forge select the map isolation then locate a small slanted structure above ground and there should be a hole on the wall. Gather up all the fusion coils, plasma batteries and power cores then throw them down the hole along with anything else of your choice. Throw a grenade down the hole and stand back! If you are going to put anything else down the hole, put that stuff down first THEN the explosives. Note: This will kill you if you are to close to the eage or the other end.

At the end of the game at the end credits just wait until they are over and then the last movie will play and this will show that the master chief is in fact alive!!!! So rejoice.

On Tsavo highway go underneath the first highway you come to (after going through the first blue barrier) and go towards the pipeline. Look for a massive beam coming down from the pipeline and try to get across using it. Use the one closest to the cliff. When you get across look for a ledge sticking out of the cliff, the skull is on that ledge. Good luck!

If you are running low on ammunition you can go over to a marine who has a different weapon than you and switch it for a different one. I know that some of you might not want a different weapon but you can swap it back and it should have more ammunition. Cool huh!

A awesome combo is a plasma pistol equiped with a magmum charge up the plasma pistol and shoot it then rapidly shoot the magmum they shud be dead very quickly.

Find an AA Wraith (for example, the one on the mission "The Covenant"). Jump on top (Don't board it), then melee it until the hatch breaks off. Melee the Brute's helmet. Line up until it says "Press RB to board." Hold RB while shooting the Brute in the head with a battle rifle. if done right, you should be able to drive the AA wraith. Don't get out unless absolutely necessary, it will explode the moment you get out. When it comes to shooting, you can shoot the green laser an infinite amount of times, while Brutes were limeted to 6, then a pause.

A good combo to use in Matchmaking or and Custom Games, some good combos are the Plasma Rifle and SMG or Spiker. And another one is Spiker and Smg. Also if you shoot someone with the Plasma Rifle 3 or 4 times you an Malee and kill them.

At the beginning of the mission in Halo. Just turn around 180 degrees and go towards the crashed pelican and you will find different guns. If you don't want new guns then leave them.

When your on the second level go till the water is close to you jump in it you won't die keep going till you are by the enemies jump up and keep shooting and then go back and try to jump out NOTE:(i found out by hitting dead people in the water and then i fell in and i kept shooting the enemies and a brute ran in the water and we fought till he died it's cool)

The best way and the way I did it to get the Achivements were you need to get a sertant amount of points for axample Ranger or Demon achivement. All you need is to activate all the gold skulls esept Blackeye and Famine because with Blackeye and Famine once you die you fail and your shields won't regenerate as fast. If you dirent know the gold skulls multiply your score making it realy easy to get those achivements.

Before u take that big jump to finish the game stop. And get out (if playing 1 player dont let the gunner see past that rock or he will kill him). And then once u get there the grunt will say some thing after u will hafta revurt from check point becase the ground falls. Heres a littel fun before u restart from check point after the ground falls there will be bars big enough to walk on and u can see how far u get before u get out of bounds.

Nearly at the end of the last mission, there will be a grunt behind a rock to your right go and do not kill him till after he talks. Be sure you do not park in front of the rock because the Arbiter will kill it. The grunt will say "Hey you the jerk store called and their all outta you..." This is not all he says but I will not spoil the rest. You must restart from the last checkpoint if you want to complete the level because all of the platforms fall.

At the point when you are fighting the 2 Scarab tanks, stay in a Hornet thoughout the whole entire battle. After you have beaten every enemy, look directly at the tower and go up the left side of the tower. Land the hornet on the left side and walk up the rest of the way. You will have to walk straight for a while than you will start going up the tower. When you get to the point where you cannot go any further you can hear a Piano playing.

Note: this can only be done when all the music has stopped before hand.

In the Mission "Halo," Go to the place where you find the last terminal. Directly opposite of the terminal is a pit. Part of the way across, there is a beam. Grenade jump to it, then get to the area further behind it. You will find a bouncing picture of a shirtless guy.

On the mission Sierra 117 get to rally point alpha continue the mission until the passage gets narrow then turn left and jump on the rocks continue along the ledge look at the wall there are cavemen!

On the level crows nest get to where the second checkpoint is kill all the bad guys go past the door keep going to the end there is a funny argument.

You have to play Forge on Construct. First, go to the pink lift (either one). Then, turn into the monitor and go down the lift to the bottom using the turbo (LT). Once at the bottom, you should see a hole type thing that you can't fit through as the monitor. So, while holding turbo the whole time, turn back to Spartan/Elite mode. You should fall through the hole. You can walk around down here, but you can still fall off and die.

*NOTE: Once down you cannot get back up unless you commit suicide.

When in the crows nest level, when in the long tunnel go the wrong way and listen to the dialogue. This changes depending on difficulty.

Go on forge get a tank drive it into a elephant turn into a robot grab the tank and turn it upside down the elephant will be upside down aswell go to flip the elephant and see what it says.

In the map Snowbound, go towards the active camo with a sniper riffle. Next look down at the ground by the active camo and you will see a little brown dot. Scope in on it and you will see what its looks like to be a duck that says "CANADA" on it.

You must be down by the water. Once there, you and your friend must get a Mongoose and a Wraith. Have your friend drive the Mongoose into the barrier. Keep accelerating and have somebody get in the Wraith. Drive behind the Mongoose inside the Wraith and use the boost. You must be close for the Mongoose to go through. Once you hit it, your friend must jump out once he sees it pass the barrier. You are now outside the barrier

Sticky grenade your monitor ally while he is human. Have him quickly change to Monitor The grenade will not detonate. Go near anyone and change back to human then back to monitor very fast. The grenade will detonate.

Use the following trick to get an unlimited Spartan laser on last level "Halo". Play through the level until you meet up with Sergeant Johnson. Shoot him until he falls down and drops the Spartan laser. Quickly pick it up and shoot it at him. Keep shooting him until he kills you. When you respawn, knock him down again and pick up his laser. He should get back up with another laser on his back. When he does, shoot him down again and pick up the new gun he drops. This laser should have unlimited Spartan ammunition. This makes it easier to destroy the Guilty Spark 343.

Jump on a marine or in co-op mode jump on your friend kill them and you will be flying. Jumping and falling off edges will put you back on the ground.

To make objects to float in Forge mode, make a tower out of two way nodes and crates. Then, delete everything except the teleporter under what you want to float. Make sure the tower ends with a two way node. This requires some time, but if done correctly you can make floating buildings that do not fall when you touch them.

To leave the level boundary, you must be at the ocean barrier (the side with the ocean). Once there, you and your friend must get a Mongoose and a Wraith. Have your friend drive the Mongoose into the barrier. Keep accelerating and have somebody get in the Wraith. Drive behind the Mongoose inside the Wraith and use the boost. You must be close for the Mongoose to go through. Once you hit it, your friend must jump out once he sees it pass the barrier. You are now outside the barrier

On the map Last Stand (Zanzibar) you can float for a little while above the ground. To do this, go into the Forge lobby. Press X and adjust the player movement settings as follows: Speed -200% to 300% Gravity -50%. Start the game when you are finished. Go to the beach. Get to the archway where the vehicles go. Turn and face the beach. You can either have someone go straight until they hit the invisible wall in the water, or take a guess. Either way, run towards the ocean. When you are about halfway to the person press A to jump in the air. When you hit the invisible wall you should float slowly down, then begin to hover just off the ground (almost as if you are walking on water.

In Forge mode, get as high as you can as the Monitor. Spawn a teleporter on the ground. Then, hug any wall still as being as high as you can and spawn another teleporter. If the teleporter beneath you is lit up as it should be, turn back into a Spartan or Elite and go through the it. You should now be outside the level boundary.

Use the following trick to get an unlimited Spartan laser on last level "Halo". Play through the level until you meet up with Sergeant Johnson. Shoot him until he falls down and drops the Spartan laser. Quickly pick it up and shoot it at him. Keep shooting him until he kills you. When you respawn, knock him down again and pick up his laser. He should get back up with another laser on his back. When he does, shoot him down again and pick up the new gun he drops. This laser should have unlimited Spartan ammunition. This makes it easier to destroy the Guilty Spark 343.

Enter Forge mode on any level where you can place both fusion coils and propane tanks (High Ground and Last Resort recommended). Place as many fusion coils as possible. Turn their run time minimum to the amount that you have placed. Do the same with the propane tanks. Make sure they are within close range of each other. If you shoot a fusion coil or propane tank, the explosion will set off any other propane tanks. When the other explosives respawn, the propane tanks that are currently flying around will usually detonate the fusion coils that have newly spawned.

You need to have a partner and be in Forge mode. Have a friend or yourself host a game. Have the person who is the host be a player and have the person who is not the host play as the Monitor. Spawn a weapon like a Brute Shot. Have the Monitor look as if he or she is going to pick it up. Do the same thing with the player. Do a countdown and have both players pick it up. On the Monitor's screen, the player's hands should have no weapon. However, that player should see the weapon in their hand. While the Monitor is still holding onto the weapon press RT and the player's arm should be ripped off, or press Y button to delete it. This may require a few attempts.

When the ship comes down to land right before u get the tank get underneath the dropping platform with the warthog. Just jump up and u start floating upwards. Sometimes u can get the platform to stop half way down.

Everyone says tripmines make the biggest explosions, well thats wrong. First have someone get in a warthog (do this on santrap) then another person spawns a bunch of power drainers, set them to instant respawn (press X twice on the object then set the minimum to the maximum) press X, X, Y as fast as you can to make you throw faster, and throw the drainers behind the warthog. When they blow and if done correctly the warthog will fly through the air from one end of the map to the other.

Go to Forge with two or more peopl, spawn any weapon. Have anyone pick the weapon up but at the same time have someone as the oracle pick the weapon up. The human players arms should be all screwed up. If you do this with the sentinel beam, it is up in the air shooting down where you aim. If you do this with the energy sword you have no weapon and when you kill someone it appears that you punch them or uppercut them in the face.

Just after you activate the second tower you have to walk out and get in either a Mongoose, Warthog, or Tank. Before you leave in one of those 3, go to the elite ship where Oracal goes into. You can jump inside of the ship and stay in there. It will fly away as it is invisible.

Note: If you go too far, the invisible barrier will knock you off the ship and you will fall to your death.

This also has to do with the elite ship but instead of just going in, make the elite that is on the turret get off and than you take control of the turret. It will fly away invisible again but it will stop at the barrier because you cant go as far as them.

Note: You have to get off of the turret but you will fall to your death again.

This can only be done in Forge Mode. Take the map Snowbound for example. Spawn every Trip Mine right on top of each other. Next press X on a Trip Mine and than press X again. Afater you have done that change the (0) on the menu to (4). After that pick up a Mine and stand in the same place and keep on throwing the (very far from you). Keep on throwing them until they blow up (the will kill you). Then you will be able to run of of bounds without the turrets shooting at you and the blue door ways will be gone. This can happen in Construct, Epitaph, Gaurdian, Snowbound, Isolation, Sand Trap, and Last Resort

Note: If done in a level with grav. lifts they will be shut off and you will not be able to float up.

This can only be done with a multiplayer on forge. When you are at a map have the person who is not the party leader press X to go to forge menu. Next the person who is not the leader must spawn a vehicle (Warthog for example) when the screen goes black. Next go over to the vehicle and the gun(s) (in this case a turret) will be missing.

These Cheats can Only be done on Legendary mode on the final level of Halo 3.

Infinite Spartan Laser ammo
To get the infinite spartan laser ammo before and after you defeat Spark, you must start the level on legendary and and travel up the large tower of flood and senitals. Once you get to the top, eliminate all the flood and senitals, this will definatly get in your way when you want to retrieve the Spartan Laser with Infinite ammo. When you are up, wait for Sergeant Johnson until he reaches you and you start to walk down the long hallways that lead to the control room. Kill him multiple times and retrieve his Spartan Laser, in which will have infinite ammo. Keep killing him right before you walk into the room with Spark and you will have them After you kill spark. This will deeply help you when in rooms with multiple enemies and such.

In high ground in forge find a turret and tell the other player too grab the turret, then turn in to the monitor and grab the turret. You will find the other player flying with the turret.