Game shark codes:

Master code "must be on"
EC8383AC 144828E4 

Infinite credits 4CE0AEFC 1456E79D 

Infinite health (player 1) 
4CE0B358 1456E79E 

Infinite health (player 2) 
4CE0B4A0 1456E79E 

Infinite ammo (player 1) 
4CE0B394 1456E79D 

Infinite ammo (player 2) 
4CE0B4DC 1456E79D