For all those Heretic players here are the cheat codes:
           (by the way whatever you do don't try IDDQD or IDKFA!):


                Cheat Keys for HERETIC by Raven/id Software


    QUICKEN---------------------> God-Mode
    RAMBO-----------------------> All Weapons
    GIMME-----------------------> Get Item
    RAVSKEL---------------------> All Keys
    KITTY-----------------------> No Clipping
    ENGAGE----------------------> Level Warp
    PONCE-----------------------> Full Health
    SHAZAM----------------------> Weapons Power-up (30 sec.)
    MASSACRE--------------------> Kill'em All
    COCKADOODLEDOO--------------> Chicken Mode <------- cool!
    TICKER----------------------> FPS Display

Enjoy!