Third-Person View
Description: Go into third-person mode while playing a single player campaign
How to: Hold down the right bumper and insert the following code: X, B, X, B, Left Analog Stick, Left Analog Stick, Y, A, Y, A, Right Analog Stick, Right Analog Stick. If done right, a message will pop up. If you want to turn off third-person mode, insert the code again.

ACE and XP Farming
[Submitted by: Cheat Masters ]
Found a spot to gain ACE and XP easily? Maybe guys are constantly dribbling down the fast lines and you can shoot them easily, or a bunch of terrorists are conveniently bunched up so you can kill them with a sack of C4.
Simply perform the actions you want for ACE and XP, then before you hit the next checkpoint, let one of those wannabe terrorists kill Bishop or Knight, forcing you to reload the checkpoint. You keep the ACE and XP you acquired (just don't turn off your system) and you can re-do that section again for more points.

TAR-21 Assault Rifle
Description: Unlock assault rifle called the TAR-21
Insert the following password when you are changing your character’s gear or firearms (you must hold the Right Bumper down when you are inserting the code):
Down, Down, Up, Up, X, B, X, B, Y, Up. Up, Y

Comcast Map
Description: Unlock a special Comcast-sponsored multiplayer map
How to unlock: Head to the in-game Extras menu, where you’ll find an option called “Comcast Gift”. Enter the code “Comcast Faster” after selecting that option, and the map will be unlocked.

Big Head Mode
Description: All characters to have big heads
How to: Pause your game during gameplay and insert the following code while holding down the right bumper:
B, X, A, Y, left stick click, Y, A, X, B, right stick click

Stronger Ragdoll Physics
Description: Stronger ragdoll physics in your game
How to unlock: Pause your game and insert the following cheat (while holding the right trigger down):
A, A, B, B, X, X, Y, Y, A, B, X, Y

Designated Killer
[Submitted by: Cheat Masters ]
Description: Get the full value of enemy kills in Story Mode and Terrorist Hunt
How to: By designating your targets. Designated targets will earn you the same EXP as if you killed the enemy yourself (instead of one-half).

Lasers Instead of Bullets
Description: shoot red and blue lasers instead of bullets (G.I. Joe style)
How to: Pause the game, hold the right bumper, and insert the following button combination:
left analog stick, left analog stick, A, right analog stick, right analog stick, B, left analog stick, left analog stick, X, right analog stick, right analog stick, Y
("[direction] analog stick" means you should press the specified analog stick in, as a button). This can also be done while playing online, but the game's host must insert the code. No other player needs to worry.

ACES Farming in France
[Submitted by: Cheat Masters ]
Description: There is an exploit in Chapter 1 The Pyrenees. Right before Gabriel Nowak defuses the bomb.
How to: Set a C4 charge on a pillar where the left gun turret will deploy. When you order Nowak to "Team Defuse Bomb", detonate the C4 to kill the enemies past the shutter; this delays Nowak being taken down (which in turn triggers more enemies to assault the room, as well as Alpha Team to come in, thus ending the stage).
As soon as you detonate the C4 (and Nowak is working on the bomb), one enemy will continuously spawn on the balcony above where Bishop and the team entered the bomb room. An emplaced machinegun will mark where that enemy will run to. Simply unload your weapon on this enemy and a replacement will spawn with no limit.
If you pay attention to your ACES menu, you can determine which points you earn. Step close (right under the turret) to get CQB points. Shoot the enemy in the head for Marksmanship points. Allow the enemy to take up the gun turret before neutralizing him for Assault Points (do not shoot him in the head or it counts as Marksmanship).
Finally, if you need to change weapons, you can always get the checkpoint before the bomb, quit to the main menu, re-outfit your PEC, then continue story mode. There are also two supply bins at the beginning of this area (the entrance to the plaza) where you can change (and refill) your weapons and gear.

M468 Assault Rifle
Description: unlock a special weapon known as the M468 Assault Rifle
How to unlock: Go to the game's main menu and hold down the Right Bumper as you insert the following code:
Up, Y, Down, A, Left, X, Right, B, Left, Left, Y

Getting ACE Points With Teamwork -- Your Teamwork
Your computer allies are great for taking out enemies for XP, but not for acquiring ACE points. Keep them back if you can handle a firefight by yourself, since enemies killed by your team will not add ACE points.
Players who are using Bishop and Knight will gain ACE points respectively in co-operative Story mode. Just remember to keep the CPU team away. This does not apply for Terrorist Hunt and adversarial Multiplayer.

Third-Person View
Description: Go into third-person mode while playing a single player campaign
How to unlock: Hold down the right bumper and insert the following code:
X, B, X, B, Left Analog Stick, Y, A, X, B, Right Analog Stick.
When done properly, a message will pop up. If you want to turn off just insert the code again.

Extra Magazine Glitch (Realistic Difficulty)
[Submitted by: Cheat Masters ]
Ammunition becomes more of a problem on Realistic. If you see a dropped weapon that's the same as one you are carrying, reload your weapon first, then trade for the dropped weapon. Trade back your weapon from the ground and you will find your reserve ammunition increased by one or two magazines (depends on the weapon).

ACE Point Actions
You can view the required actions for ACE points when you pause the game. They are:

Assault ACE Points
+3 Kill an enemy or player behind cover with penetrating weapons.
+3 Kill an enemy or player with C4 (it must be C4)
+2 Kill an enemy or player who is using a mounted machinegun
+2 Kill an enemy or player with a frag grenade or breaching charge (i.e., something that's not C4)
+2 Kill an enemy or player who is using a riot shield

Marksmanship ACE Points
+3 Kill an enemy or player at long range (about the size of your targeting circle at its widest diameter)
+3 Kill an enemy or player when they are on a rope (fast rope or rappelling)
+2 Kill an enemy or player while you are rappelling
+2 Kill an enemy or player who is sprinting
+1 Kill an enemy or player with a headshot (any weapon, although a long distance headshot will result in a long distance kill instead)

Close Combat ACE Points
+3 Kill an enemy or player at short range (their height should be a third to half of the size of your screen on either standard or hi-def)
+3 Kill an enemy or player who is stunned or flashbanged (vision impaired)
+3 Kill an enemy or player by blind-fire (this range may be slightly more than the short range kill distance)
+3 Kill an enemy or player from behind (distance may change this to a long range kill)