Extreme Assault

Type "levelx" and one space in the main menu to activate the cheats...

alt+1:ammo
alt+2:guns
alt+3:energy
alt+4:immortality
alt+6:end level
alt+7:destroy all enemys
alt+8: copter
alt+9: tank.

Note: If 'levelx' doesn't work, try typing 'oh dear'....
(Information from Cheat Machine)