At the Title screen, hold L + R and enter the following cheats:

Play as Nicole:
Left, Up, Down, Up, B, Up.

Hyper punch mode:
Left, Right, B, Up, B, Right, Left.

Unlimited canteen:
Left, X, B, Down, X, A, X, B

Original Pitfall:
B, B, Left, Right, B, X, A, Up, B. You can find it at the New Game screen.

Original Pitfall 2:
Left, Right, Left, Right, Y, Y, Y. You can find it at the New Game screen.

Thanks to Revolution readers Harry and june!