Press ~ then type in the following of the codes.

Kariya               Max out Ammo
corbet or stilllife  Be invisible
drury                Get full ammo
roy                  invincibility
domi                 artiltery strik
thetrooper           God Mode            
diewithyourbootson   Unlimited Ammo      
sunandsteel          Reload Ammo  
revelation           Artillery Rounds 
Bozo                 Bozo Mode  
roy                  Invincibility  
fly_up               Fly up   

Commands:
/s:                  Save Scores
/d:                  Reload From Directory, Not PIF file.
/p filename:         Play Demo
/sys:                System Info.
/?:                  Display Command Options
/r:                  Record Demo In 1-Player Mode.  



Hints

Magical Reload:
If you save your Mission, when you reload the Mission, your Ammo is back up tp
Full... 

Loading & Saving:
Type in savegame or loadgame to do one or the other.