Stalactite game:

Enter BRGR as a password for a secret game called Stalactite. The 
game is playable only on revison A 3DO motherboards and will lock 
on newer machines. The object of the game is to avoid the balls 
and falling stalactites in order to survive as long as possible. 

Hidden picture:

Press LS + RS when animated introduction starts and hold both 
buttons through the Start Game screen to display a hidden picture. 

Dark level:

Enter HHFL as a password to access a completely dark level. Although 
your character can move or shoot, nothing will appear on-screen.