Here are a few cheats to get you started
Enter these at the level select screen:
Invincibility - R,Z,C down,R,R.
Infinate Ammo - C up,Z,C left,Z,C left.
High Powered 9mm Pistol - R,L,C down,C up,C down.
Uzi with 30 rounds - C right,C left,C right, C down,C down.
7.65 Silenced Pistol - C up,L,C right,C left, C down.
Mini-Missle Launcer
Press R,L,C-left,C-right,C-down.
Red Dress
As soon as you get to the main menu, press z ten times very fast, the screen will turn red if you have done it correctly. The hold the a and b buton, and at the same time push start. Tom Cruize will have infinite eveything, and have a red dress throughout the entire game.