Cheats:

 The famous 'jassica16' code: Type it in anytime during the game
 to enable 'cheat mode'. press F10 to get all the good weapons,
 ammo, & items. Be sure to drop whatever weapons you have before
 hitting F10 to insure getting the good stuff. Press 'CTRL F10' to
 become invincible.

 Start parameter:

 -debug    Runs debug mode other than that ???
 -setver   not sure not tested
 -vesatest sounds pretty obvious not tested
 -asylum   start up says "Running Enhanced Mode (NOT!)"
 -skill    sets default skill to (1-4)  -skill x
 -warp     warps you to a mission (1-?)  -warp x
 -mapoff   start up comes up with an error and locks
 -egg      see mapoff
 -demo     this is documented runs intro over and over