Infinite Ammo:In single player mode pause the game and enter the following: D-pad Up, D-pad Down, D-pad Left, D-pad Down, D-pad Down, D-pad Left, D-pad Down, D-pad Down, D-pad Left, D-pad Down, D-pad Down, D-pad Down, D-pad Left, D-pad Right
Invincibility: In single player mode, pause the game and enter the following code: D-pad Up, D-pad Up, D-pad Up, D-pad Left, D-pad Down, D-pad Down, D-pad Down, D-pad Left, [dapd:n], D-pad Up, D-pad Up, D-pad Left, D-pad Right

All "button press" cheats are courtesy of CVG