Just finished re-playing Wolfenstein 3D using NewWolf a OpenGL (video) and SDL (audio) rewrite of the engine. A little issue is that after killing each of the Boss's it doesn't end the map but, whatever you know you did it. It's a dead project but, it is the best Wolf3D engine rewrite.
The game is still hard, fun, and can get your blood pumping when you come around a corner and face down the Blue machine-gunner. And who doesn't like killing Nazi's (ah when good and bad was so black and white), except maybe German's. The map (TAB) gives you a little bit of a cheat at finding secrets. Be careful as you might go bleary eyed through some of the maps where the secrets are like impossible to get to all of them.
You'll be amazed by some of the great design and gameplay mechanics that were ahead of the games time, including enemies that patrol, specialized sounds (e.g. things farther away are softer than those that are close up, also things on the left and right are actually setup that way). You might want to search for the original game, not sure if the full version is legal to download, so that you can also revel in the nostalgia inducing game with NewWolf.