Codes
For each of the following codes, pause the game and hold down L1 and L2 together for at least 10 seconds. While still holding L1 and L2, enter each code.

Extra Ammo--Down, Right, Circle, Left, Right, Circle.
Extra Lives--Left, Down, Right, Triangle, Square, X, Circle.
Extra Bombs--R1, R2, X, Triangle, Square, Circle, R1, R2, Circle, Circle, Square.
Health--Right, Right, Left, Down, Down, Up, Triangle, Circle.
Level Select--Up, Right, Down, Left, Triangle, Circle, X, Square, X, Triangle, Square, Circle.
Level Skip--X, R1,Triangle, R1, Square, Circle, R2, R2, X, Square, Triangle, X.
Weapon Power Up--Down, Right, Down, Right, Triangle.

Splattered corpse
To move around as a walking corpse simply equip the health option cheat and pause the game after dying and refill your health.Now you should be a splattered corpse. However your actions are limited,but this is a good thing to try on level 6 or on a 2-player game.