Fading Suns - In my opinion one of the most fun sci-fantasy settings out there. I love the combination of medieval culture and bits of rare high technology, the intrigue and factions involved, the alien cultures, and psionics and theurgy as well as evil "magic". There are rumors that a new edition will come out soon.
Deadlands Classic - I have the entire collection. I love the weird western genre, the mix of western, horror, and steampunk elements, and the alternate history aspects of the game. The system can be clunky at times, but packs in a lot of flavor with the use of poker chips and cards.
Unknown Armies - I loved the few sessions I played of this. An interesting modern occult setting, with its own unique twists. One of my favorite aspects were pages full of short rumors that may or may not be true. They made for excellent adventure hooks or weird things to have NPCs talk about.