Oh, here's a random interesting one:
Five Nights at Freddy's, in ROM hack form.
Not sure how it'd work best, but there are two awesome ways that game could be done as a hack or homebrew:
1. A fairly accurate clone of the mechanics using the Sega CD or something. Heck, this game could probably even work on the CD-i to be honest. Or even a more traditional system, if the scenes were significantly colour reduced.
2. A level in another game hack based on it. It was a few years too late for a Mushroom Kingdom Fusion level, but come on, someone so has to make a game where your favourite characters are adventuring through the pizza parlour and dodging/defeating the rogue animatronics. Would it make a mockery of the game's tone? Oh sure, but come on, Mario or Sonic or Link or Mega Man or whoever going in 'all guns blazing' would be hilarious. Especially if it had the MKF style guns, with the Metal Slug voices shouting 'heavy machine gun!' or 'rocket launcher!' respectively.