Cheat List:
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

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, R BUTTON, L BUTTON, Y, X, X

M7 Turned Frag Launcher - R BUTTON, L BUTTON, RIGHT, RIGHT, LEFT, LEFT, RIGHT, RIGHT, L BUTTON, R BUTTON, X, Y

Crossbow Turned Frag Launcher - LEFT, RIGHT, RIGHT, LEFT, X, Y, R BUTTON, L BUTTON, 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 - R BUTTON, X, R BUTTON, Y, R BUTTON, LEFT, R BUTTON, RIGHT, R BUTTON, L BUTTON, L BUTTON, X, L BUTTON, Y, L BUTTON, LEFT, L BUTTON, RIGHT, X

Watch End Cinema - L BUTTON, R BUTTON, X, X, LEFT, R BUTTON, R BUTTON, X, X, L BUTTON, X