ADOOM
(id Software / GT Interactive, 1993)

Cheat Codes (type during gameplay):

  IDDQD        - Full health (God mode)
  IDDT x1      - All maps
  IDDT x2      - All maps and monsters
  IDKFA        - Full ammo, all weapons and keys
  IDCLEVxx     - Warp to level xx
  IDCHOPPERS   - Locked
  IDSPISPOPD   - Walk through walls
  IDCLIP       - Clipping mode ON/OFF
  IDMYPOS      - Display coordinates
  IDBEHOLD     - Then press one of these keys:
                   I - Invulnerability
                   V - Invisibility
                   S - Berserk Pack
                   R - PowerUp
                   A - Area map
                   L - Light

(Source: OLLIVision)