Cheat mode 
Pause the game and press 
L, Left, R, Right, X, X, Down, Down, R, L.

Level select 
Pause the game and press 
Up, Down, Up, Down, Up, Down, Left, Right, Right, Y.

Level skip 
Pause the game and press 
Y, Y, X, X, L, R, Down, Down, Up, Up. 

Extra lives 
Pause the game and press 
A, B, X, Y, L, R, Up, Down, Left, Right.

First person view 
Pause the game and press 
L, Left, R, Right, X, X, Down, Down, R, L.

Extra credits 
Pause the game and press 
A, B, Left, A, B, Right, B, A, Down, R. 

Grenades 
Pause the game and press 
Down, Down, Down, Down, Down, Up, Up, Up, Up, R.

Shields 
Pause the game and press 
Up, Down, Left, Right, X, Up, Down, Left, Right, Y.

Instant victory 
Pause the game and press 
L, R, L, R, Left, Right, Left, Right, Y, X.