Here are some codes for Heretic. Note: type -ravpic at startup and use F1 for screen shots.
QUICKEN - God Mode
RAMBO - All Weapons/Ammo
GIMMExx - Artifacts (a-j) (1-9) *d does not work*
SKEL - All Skeleton Keys
RAVMAP - Changes Map Mode (in map mode)
KITTY - Toggle Clipping
ENGAGExx - Level Warp (episode/map)
PONCE - Full Health
SHAZAM - Toggles Weapon Power
MASSACRE - Kills ALL monsters on level
COCKADOODLEDOO - Turns yourself into a chicken
IDDQD - Instant Death
IDKFA - No Weapons/Ammo
