Waves of the Undead is a difficult and short full megawad, most maps are enemy filled in one way or another, the main focus is really the enemies and finishing the level. There's a lot of shotgunners, barons, knights and revenants. Anyway, it probably only runs on ZDoom/Boom-compatible ports.. Also, have a good computer, unlike mine, which lagged in some places with many enemies. It uses the default Doom II IWAD. Also, there's no crouching, jumping, or mouselook required.