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

Half Damage - SQUARE, SQUARE, CIRCLE, CIRCLE, LEFT, LEFT, RIGHT, RIGHT, CIRCLE, CIRCLE, SQUARE, SQUARE
Bulletproof - LEFT, RIGHT, RIGHT, LEFT, SQUARE, CIRCLE, CIRCLE, SQAURE
Invincibility - LEFT, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, LEFT, SQUARE, SQUARE
Infinite Ammo - SQUARE, CIRCLE, SQUARE, CIRCLE, SQUARE, CIRCLE, SQUARE, CIRCLE, LEFT, CIRCLE, SQUARE, CIRCLE, SQUARE, CIRCLE, SQUARE, CIRCLE, SQUARE
One-Shot Kills - CIRCLE, LEFT, RIGHT, RIGHT, LEFT, CIRCLE, R2, L2, CIRCLE, SQUARE, SQUARE
M7 Turned Frag Launcher - L2, R2, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, R2, L2, SQUARE, CIRCLE
Crossbow Turned Frag Launcher - LEFT, RIGHT, RIGHT, LEFT, SQUARE, CIRCLE, L2, R2, SQUARE, CIRCLE, LEFT, RIGHT
Big Weapons - SQUARE, SQUARE, SQUARE, SQUARE, CIRCLE, CIRCLE, CIRCLE
Big Feet - RIGHT, RIGHT, RIGHT, LEFT, RIGHT, LEFT, RIGHT, LEFT, LEFT, LEFT
Skip Cut-Scene - L2, SQUARE, L2, CIRCLE, L2, LEFT, L2, RIGHT, L2, R2, R2, SQUARE, R2, CIRCLE, R2, LEFT, R2, RIGHT, SQUARE
Watch End Cinema - R2, L2, SQUARE, SQUARE, LEFT, L2, L2, SQUARE, SQUARE, R2, SQUARE