Cheats:

 These cheats are for the 3Dfx version only! Hold [Ctrl][Alt][Shift]
 and then type:

 su - Invulnerability on/off
 is - Unlimited ammo on/off
 oo - Heat tracking on/off
 it - Destroy current target by nuking it
 re - Destroy current target
 in - Gives you jump jets
 cr - Unlimited jump jet juice
 li - Ends mission succesfully
 be - Enables Free-Eye mode