During game play type in the following codes and then press 'Enter'. Unlock God Mode:
Invulnerability

Complete Level:
Deadlineisnear

Unlimited Lives:
Igonnaliveforever

Unlock ALL Weapons:
Showmetheweapons

Unlock ALL Missiles:
Moremoreweapons

Unlock ALL Powerups:
Glitteringprizes

End Game:
Diediediemydarling