God Mode:
Pause the game, and then hit: Left, Right, Left, Right, L1, R1, L1, R1.

Extra Continues:
Pause the game, and then hit: X, Up, Down, Triangle, Circle, Circle, Circle, L1.

Extra Lives:
Pause the game, and then hit: Square, Down, Right, Circle, Square, Left, Up, X.

First-Person View:
Pause the game, and then hit: L1, Up, Left, Triangle, X, L2, R1, L2.

Level Select:
Pause the game, and then hit: Up, Down, Right, Left, X, X, X, Triangle