During gameplay, press START and enter any of the following codes:

Half Damage - X, X, Y, Y, LEFT, LEFT, RIGHT, RIGHT, Y, Y, X, X
Bulletproof - LEFT, RIGHT, RIGHT, LEFT, X, Y, Y, X
Invincibility - LEFT, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, LEFT, X, X
Infinite Ammo - X, Y, X, Y, X, Y, X, Y, LEFT, Y, X, Y, X, Y, X, Y, X
One-Shot Kills - Y, LEFT, RIGHT, RIGHT, LEFT, Y, BLACK, WHITE, Y, X, X
M7 Turned Frag Launcher - BLACK, WHITE, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, WHITE, BLACK, X, Y
Crossbow Turned Frag Launcher - LEFT, RIGHT, RIGHT, LEFT, X, Y, BLACK, WHITE, X, Y, LEFT, RIGHT
Big Weapons - X, X, X, X, Y, Y, Y
Big Feet - RIGHT, RIGHT, RIGHT, LEFT, RIGHT, LEFT, RIGHT, LEFT, LEFT, LEFT
Skip Cut-Scene - BLACK, X, BLACK, Y, BLACK, LEFT, BLACK, RIGHT, BLACK, WHITE, WHITE, X, WHITE, Y, WHITE, LEFT, WHITE, RIGHT, X
Watch End Cinema - WHITE, BLACK, X, X, LEFT, BLACK, BLACK, X, X, WHITE, X