Cheat Mode:
To activate the cheats at the main menu screen hold L2 and R2 down and press Left, Down, Right and Up. If you have done the cheat correctly then ti will say CHEATS ON at the bottom of the screen. It will give you invincirbility and unlimited ammo.

GameShark Codes

Rapid Fire Press X         d40605740040
                           800605740001  

Super Jump Press Triangle  d40605500010
                           800605500001  

Thanks to Revolution readers Ahpschepsut and Michael!