Interesting weapons, unusual monsters, and (with one exception) entertaining boss fights--Undying is a creepy and enjoyable horror FPS. The graphics hold up well, and the sound effects are fantastic. The story, however, is rather pedestrian, with a bunch of loose ends and a garbled ending. Still, well worth a play through for any horror buff.
I paid about $2.50 for this, and I feel ripped off. The only thing that scared me about this game was how bad the interface was. Trying to do something as simple as break a crate is an exercise in frustration, as the actions don't map well to mouse movement. Only get this if you have the patience to master the bizarre control scheme.