All weapon upgrades:
Press Start to pause game play, then hold L and press Up(2), Down(2), Left, Right, Left, Right, X, Circle.

Giant scythe or whip:
Press Start to pause game play, then hold L and press Triangle, Square, X, Circle, Up, Left, Down, Right.

Refill ammunition:
Press Start to pause game play, then hold L and press Triangle(2), X(2), Square, Circle, Square, Circle, Down, Right.

Unlimited ammunition:
Press Start to pause game play, then hold L and press Triangle(2), X(2), Square, Circle, Square, Circle, Right, Down.

Invincibility:
Press Start to pause game play, then hold L and press Up(2), Down(2), Left(2), Right(2), Square, Triangle. When you exit the start menu, "Can't touch this" will appear to confirm correct code entry.