Wikipedia
DoomRL
DoomRL (or Doom, the Roguelike) is a roguelike video game for Microsoft Windows, Linux and Mac OS X, whose setting is based on the first-person shooters Doom and Doom II. It was created by Kornel Kisielewicz using Free Pascal and SDL.
Discussion participants of 1UP.com's " Retronauts" podcast declared DoomRL to be "quite possibly, the greatest Doom spin-off ever".