Cheat mode
Enter the cheat menu from the options screen. Highlight one of the following cheat options and enter the corresponding code to unlock it. A sound will confirm correct code entry. Press X to exit the cheat menu. Note: Press Circle to exit the cheat menu to disable all active codes.

Always Invisible
Press L, Left, Right, Square, Triangle, R while that option is highlighted at the cheat menu.

Insta Gib
Press L, Square, Triangle, Right, Triangle, R while that option is highlighted at the cheat menu. 

Max Players
Press Right, Left, Right, Left, Right, Left while that option is highlighted at the cheat menu. 

Mortar Only
Press Triangle, L, Square(2), Right, Left while that option is highlighted at the cheat menu. 

No Auto Heal
Press Start, Right, Left, Select, Right, Square while that option is highlighted at the cheat menu. 

Pick Up Double Time
Press Square, Right, Triangle, Right, R, L while that option is highlighted at the cheat menu. 

Team Special Recharge
Press Right(2), Left. Square, R, L while that option is highlighted at the cheat menu. 

Unlimited Ammo
Press Left, R, L, Triangle, Right, Square while that option is highlighted at the cheat menu.