Invincibility
Press Left, Square, Up, Triangle, Right, Circle, Down, X at the cheat screen.

Unlimited ammunition
Press Down, X, Left, Circle, Down, X, Left, Circle at the cheat screen.

Slow motion mode
Press Left, Square, Up, Triangle, Left, Square, Up, Triangle at the cheat screen.

Invisibility
Press Left, Square, Right, Circle, Left, Square, Right, Circle at the cheat screen.

Alien mode
Press Up, Triangle, Up, Triangle, Up, Triangle, Up, Triangle at the cheat screen.

Xen gravity
Press Up, Triangle, Down, X, Up, Triangle, Down, X at the cheat screen.