Extreme Assault
When you are at the main menu, type 'levelx' and then press the spacebar. Or You can, type 'oh dear' and hit the spacebar again.
Alt-0 Speed
Alt-1 Full ammunition
Alt-2 Upgrade weapons
Alt-3 Restore energy
Alt-4 God mode
Alt-6 End mission
Alt-7 Deactivate enemies
Alt-8 Helicopter