Enter the following as Passwords:

LEVEL 1 : JUNGLEWAR
LEVEL 2 : BUCCANEER
LEVEL 3 : DETONATE
LEVEL 4 : AFTERSHOCK
LEVEL 5 : BLITZKRIEG
Bonus   : LIGHTNING

Super cheat:
     Enter CHEESYPOOF as a Password for unlimited ammo, unlimited fuel
and invincible armor.

Other Passwords:
OLDSCHOOL - old view 
AFTERSHOCK - nuclear detonation
UNLEADED - unlimited fuel 
GUNSRUS - unlimited ammo
CHAINMAIL - unlimited armor