Hide Weapon, Show Coordinates & Camera Modes. 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.

LB = Left Bumper
RB = Right Bumper
LS = Click in on Left Analog Stick
RS = Click in on Right Alalog Stick

Toggle Hide Weapon: LB + RB + LS + A + DOWN [D-PAD]
Toggle Pan-Cam / Normal while Show coordeinates is enabled: [HOLD LS + RS] Press Left on D-Pad
Toggle Show Coordinates / Camera Mode: LB + RB + LS + A + UP [D-PAD

Landfall (20 points): Finish the first mission of the Campaign on Normal, Heroic, or Legendary.
Holdout (20 points): Finish the second mission of the Campaign on Normal, Heroic, or Legendary.
The Road (20 points): Finish the third mission of the Campaign on Normal, Heroic, or Legendary.
Assault (30 points): Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary.
Cleansing (30 points): Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary.
Refuge (30 points): Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary.
Last Stand (40 points): Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary.
The Key (40 points): Finish the eighth mission of the Campaign on Normal, Heroic, or Legendary.
Return (50 points): Finish the final mission of the Campaign on Normal, Heroic, or Legendary.
Campaign Complete: Normal (125 points): Finish the Campaign on Normal.
Campaign Complete: Heroic (125 points): Finish the Campaign on Heroic (unlocks achievement for Normal, if not earned).
Campaign Complete: Legendary (125 points): Finish the Campaign on Legendary (unlocks achievements for Normal and Heroic, if not earned).
Iron (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Black Eye (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Tough Luck (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Catch (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Fog (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Famine (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Thunderstorm (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Tilt (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Mythic (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Graduate (10 points): Earn 5 EXP or finish 10 games to complete the requirements for basic training (Online).
UNSC Spartan (15 points): Earn your Sergeant rating to be recognized as a true Spartan (Online).
Spartan Officer (25 points): Advance to the Spartan Officer ranks (Online).
Two for One (5 points): Score a Double Kill with a single Spartan laser shot in a ranked free for all playlist (Online).
Too Close to the Sun (5 points): Destroy an enemy Banshee with the Spartan laser or missile pod in a ranked playlist or in campaign.
Triple Kill (5 points): Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online).
Overkill (5 points): Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online).
Lee R Wilson Memorial (5 points): Score 5 grenade sticks in any ranked free for all playlist (Online).
We're in for some Chop (5 points): Destroy an enemy vehicle with equipment in a ranked playlist or in campaign.
Killing Frenzy (5 points): Kill 10 enemies without dying in any ranked free for all playlist (Online).
Steppin' Razor (5 points): Score a Triple Kill with the sword in a ranked free for all playlist (Online).
Mongoose Mowdown (5 points): Splatter an enemy with the mongoose in a ranked free for all playlist (Online).
Up Close and Personal (5 points): Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online).
Fear the Pink Mist (5 points): Kill 5 enemies with the needler in a ranked free for all playlist or in campaign.
Headshot Honcho (5 points): Kill 10 enemies with headshots in a ranked free for all playlist or in campaign.
Used Car Salesman (5 points): Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign.
Marathon Man (40 points): Locate and access all Terminals in the Campaign.
MVP (5 points): Earn the MVP in any ranked playlist (Online).
Maybe Next Time Buddy (5 points): Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online).
Guerilla (10 points): Score over 15,000 points in the Campaign meta-game on the first mission.
Demon (10 points): Score over 15,000 points in the Campaign meta-game on the second mission.
Cavalier (10 points): Score over 15,000 points in the Campaign meta-game on the third mission.
Askar (10 points): Score over 15,000 points in the Campaign meta-game on the fourth mission.
Exterminator (10 points): Score over 15,000 points in the Campaign meta-game on the fifth mission.
Ranger (10 points): Score over 15,000 points in the Campaign meta-game on the sixth mission.
Vanguard (10 points): Score over 15,000 points in the Campaign meta-game on the seventh mission.
Orpheus (10 points): Score over 15,000 points in the Campaign meta-game on the eighth mission.
Reclaimer (10 points): Score over 15,000 points in the Campaign meta-game on the final mission.

There are various Halo Armor that you can unlock while playing the game. Each is slightly different than the last.

Body Pieces: Spartan marked with (S) and Elite marked with (E).
(E) Ascetic Body: Unlock "Up Close and Personal" Achievement
(E) Ascetic Head: Unlock "Steppin' Razor" Achievment
(E) Ascetic Shoulders: Unlock "Overkill" Achievment
(E) Commando Body: Unlock "Triple Kill" Achievement
(E) Commando Head: Unlock "Overkill" Achievment
(E) Commando Shoulders: Unlock "Killing Frenzy" Achievment
(E) Flight Body: Complete Tsavo Highway On Herioic or Legendary
(E) Flight Head: Complete Campaign mode on Heroic difficulty.
(E) Flight Shoulders: Complete The Ark on Heroic difficulty or higher.
(S) EOD Body: Complete Tsavo Highway on Legendary
(S) EOD Head: Complete Campaign mode on Legendary Difficulty
(S) EOD Shoulders: Complete The Ark on Legendary difficulty
(S) EVA Body: Complete Tsavo Highway on Normal or higher
(S) EVA Head: Complete Campaign mode on Normal
(S) EVA Shoulders: Complete The Ark on Normal difficulty or higher.
(S) Mark V Head: Unlock "UNSC Spartan" Achievment
(S) ODST Head: Unlock "Spartan Graduate" Achievment
(S) Rogue Head: Unlock "Spartan Officer" Achievment
(S) Scout Body: Unlock "Too Close to the Sun" Achievement
(S) Scout Head: Unlock "Used Car Salesman" Achievment
(S) Scout Shoulders: Unlock "We're in for Some Chop" Achievment
(S) Security Head: Earn 1000 Gamerscore points.
(S) Security Shoulders: Earn 250 Gamerscore points.

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.

Black Eye Skull: 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.

Iron Skull: 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.

Mythic Skull: 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.

Blind Skull: When you get to the area where you see the Phantom overhead (one of the marines will point it out) jump over the rocks and keep following the path on the right. When you get to the cliff there will be a rock over of the side. The skull is on the end of the rock. Note: This skull has to be Activated before you start a Campaign map.

Grunt Birthday Party skull: How to find: Right after the first objective, while en route to the barracks, you will fall down onto a pipe. At the end of this pipe, look over the edge to see a small space a few feet below you. You must simply drop over and as quicly as you can, pull back to land under the floor you were just on. After that, the skull will be at the end.

Catch Skull: Mission: The Storm. You can get this by performing a grenade jump off a warthog, or grab a ghost and go back to the ramp from which you first came out, using the ghost to push a big square crate back over to the front of the silo pod that the skull is on top of, then use the box as a place to jump from.

Cowbell Skull: Level: The Ark Location: 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.

Famine Skull: Mission: The Ark. When you first go into the valley to the right after the wrecked phantom, look to your left where you will see a huge boulder. Use a ghost and get to the side of the boulder that is closest to the bridge overhead. It is easy to pilot the ghost up the side of the wall using the thrust. To get the skull, pilot 2 ghosts up the wall to the top of the bridge and stack them one on top of another next to the beam where the skull is placed. Simply jump from the top of the ghosts towards the skull and land on the beam.

Fog Skull: Mission: Floodgate. As you are walking down from the anti-air gun you destroyed in the previous mission, you encounter a ramp (next to a missile launcher). Around this ramp, you hit a checkpoint. At this point, you should also hear a marine yelling, "There! Over There!". Look up and to the right, directly at the roof of the building next to the missle launcher. There is a single flood form (not to be mistaken with the two other flood forms jumping in front of you) which is holding the skull. Kill him before he jumps, and he will drop the skull down to the ground where you can retrieve it. Too early, and the skull will get stuck on the roof though, so just time it carefully.

Thunderstorm Skull: Mission: The Covenant. After you shut down tower 1 and get access to the hornet, fly to tower 2 (the one the arbiter shut down). While walking up the stairs, go to the middle part that connects both and there should be a stair leading up to a platform where the skull is.

Tilt Skull: 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.

Tough Luck Skull: 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.

Catch Skull: From the start of The Storm level, go through until you go outside again. When you go outside look straight across there is a small round building straight out there, the skull is on top. In order to get up there you can either use a warthog as a platform or grenade-jump. DO NOT destroy the wraith near the door or the skull will disappear.

IWHBYD Skull: Mission: The Covenant. To get this, get to the room where you "fight" the Prophet of Truth. Let the Arbiter kill him, turn around, and kill all the Flood here as well; makes it a LOT easier. With all obstacles out of the way, you need to jump through the Halo holograms here in a specific order: 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 4. When you jump through the final hologram, they all light up in a sequential pattern. The Skull will be at the end waiting for you right before the energy bridge leading to Truth's corpse.

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

The 7 Terminals
The Ark:
1. Start the mission and once you enter the first building take a left into another door and now you should be in a curved corridor. On the inside is a Terminal.
2. After activating the bridge to let your comrades accross the gap, do a 180 and you should see it. (it does not open until you activate the bridge)
3. In the third building after defeating the scarab, kill the group of sleeping covenant, then follow the corridor downwards. Once you reach a door in front that is locked, immediately on the left there's an open door. Go through and walk straight off, then do a 180 to find a secret room. It is in there.

The Covenant:
1. When in the first tower standing on the lift, face the access panel and turn left. Jump over and it's right there.
2. Land your hornet on the second tower, walk towards the entrance but when you see the locked door, do a 180. Should be right in front of you.
3. When in the third tower standing on the lift, face the access panel and turn right. Jump over and it's right there.

Halo:
1. After reaching the end of the first cave, hug the right wall and you will see a building. Jump up onto the walkway and hang a left once inside. It's right there.