Invincibility:
Go to the cheat menu and press Left, Square, Up, Triangle, Right, Circle, Down, X.

Endless ammunition:
Go to the cheat menu and press Down, X, Left, Circle, Down, X, Left, Circle.

Invisibility:
Go to the cheat menu and press Left, Square, Right, Circle, Left, Square, Right, Circle.

Slow-motion Mode:
Go to the cheat menu and press Right, Square, Up, Triangle, Right, Square, Up, Triangle.

Alien Mode:
Go to the cheat menu and press Up, Triangle, Up, Triangle, Up, Triangle, Up, Triangle.

More Gravity:
Go to the cheat menu and press Up, Triangle, Down, X, Up, Triangle, Down, X.