Shadow Gunner: The Robot Wars Cheats (PSX)

Hold 'Select' at the Main menu and quickly press Triangle, Triangle, Triangle and enter
the following codes to unlock the corresponding effect.

Unlock Level Select: 

Press Square, X, Square, Triangle, X, Triangle, Circle, Square. Start a new game and hold
'Select' and press Left or Right at the 'Mission Introduction' screen to choose a new
starting level.

Unlock Invincibility:

Press Triangle, Circle, Circle, Triangle, Circle, Square, X, X.