Also, for games that I'm not playing, but like in my collection:
Fabula Ultima - JRPG inspired!
Mazes - cool system where every class rolls a single die type for all rolls. So Rouge d6, Mage d4, etc.
Hackmaster - Packed full of unique mechanics that I homebrew into other games. Namely, combat without "rounds".
Star Wars RPG (Revised, Expanded, Updated) - Awesome d6 SW system that's free to download. Not sure if I can link, so just Google!
Shadow of the Demon Lord - One of the most well written d20 games I've ever played. Don't like the tiny supplement format he uses though.
Rifts - The original corebook has so many iconic pictures and clever ideas. I've had my copy since I was 8 and will take it to the grave with me!