Doom 2 [DeathMatch] Game Cheats
There seems to be something strange with the IDDT cheat (the "map-mode"). It works on the Nightmare level, whereas the others don't. But the real interesting thing is : Hold [Alt] while typing IDDT 3 times, on the map screen in deathmatch mode enables you to see all monsters and your human enemies! This may not work on all versions (surely not on version 1.9 and above) but we tought it was too important not to mention.