Back in 2010, a chap named Paul Schneider brought Doom II fans an exciting mod in the form of Unloved [official site]. A traipse through the classic shooter several shades darker (way more than fifty shades) than fans were used to, it was an exercise in serving up entrails as floors and chunks of flesh scattered throughout each level.
Most importantly, it was good. It could have become its own game, honestly. Oh, wait. It looks like it has! Unloved has broken out on its own as a fully-fledged horror shooter after escaping the confines of Steam’s Early Access. It’s available in full now, in fact, and looks like it’s well worth trying.