Expendable Cheat Codes:

-First Person View
Pause the game and press L, Left, R, Right, X(2), Down(2), R, L.

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

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

-Grenades
Pause the game and press Down(5), Up(4), R.

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

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

-God Mode
Pause the game and press Up, Down, Left, Right, L, R, Left, Right, Start.

-Level Skip
Pause the game and press Y(2), X(2), L, R, Down(2), Up(2).

-Level Select
Pause the game and press Up, Down, Up, Down, Up, Down, Left, Right(2), Y.