I've also played World Tree (an obscure furry RPG that has mechanics I'm not happy with and would like to convert to D20) and World of Darkness and its assorted trappings. I own more RPGs than I'll ever be able to play, likely.
I don't get much opportunity to play non-d20 stuff these days (stupid d20 focused group )
BUT when I can:
Shadowrun 3E (for now): My game of choice, I run a game for my Boston friends when I'm up and there's time, as well as at GameDays and I play when I go home to SK.
HARP: Played it once, enjoyed it and would like to play it more...but I'm unlikely to except at GameDays.
Exalted: Played it once, have a friend who loves it, so opportunities may arise...
Things I'd like to play:
Since others have mentioned it BattleTech mostly. I played a lot in high school and miss it...still have some Mechs to paint
Shadowrun is the only non-d20 game I play consistently. I've played GURPs, Seventh Sea and In Nomine in the past but never for an any considerable period of time. I use to play TSR's Marvel RPG reguarly.