Press TILDE (~) key during gameplay and enter the following for cheats

please god:Invincibility / God Mode
please fly: Free Flight
please ghost: No Clipping
please giveall:Give All Items
please open:Open All Doors
please invisible:Invisibility
please refresh:Refreshes Health
please killall:Kills all enemies visible on screen
please tellall:Gives you all messages and intelligence data from Netricsa

Type the above codes again to deactivate the cheats.

More Cheats : Press F1 Key to access the game console. Type any of the cheats below and press F1 again to return to the game.

cht_bGod – God mode/Invulnerability
cht_bInvisible – Invisibility
cht_bGiveAll – Give All Weapons
cht_bCopyCheatingPlanet – Activate All Cheats
cht_bGhost – Ghost mode (walkthrough walls)
cht_bRefresh – Full Health 200
cht_bFly – Flying mode

Demo Cheat Codes
At the Main Demo Screen (where you can select Single Player, Demo, etc.) Hit the Tilde (~) Key to bring up the console. Type in one of the following:
To see a list of variables that can be changed, type in the following:
ListSymbols()