Gunship 2000 Codes -

Invincibility:
Hold L1 + L2 + R1 + R2 during the entire loading screen with the helicopter that appears after receiving the mission orders. The word "Cheat" will appear in the upper left corner of the mission screen to confirm correct code entry. Note: The helicopter can still crash into mountains when this cheat is enabled.

Unlimited ammunition:
Hold L1 + L2 + R2 + X during the entire loading screen with the helicopter that appears after receiving the mission orders. The word "Cheat" will appear in the upper left corner of the mission screen to confirm correct code entry.