Traveller 4th edition - Great fun, but starship design was a headache. Haven't played in years.
GURPS - Another game that we enjoyed. Actually thinking about picking up the 4th edition, and maybe running a Rifts-style game with those rules.
Rifts - I really like the setting, but the system needs a massive re-write IMHO, and the power creep needs to be eliminated. The OCC's in the main book need to be just as powerful and viable as those presented in the World Books and Supplements.
Palladium Fantasy - Not so much a problem as Rifts, but could stand a good bout with an editor and some rule clean-up.
Star Wars d6 - Haven't run this system since SW d20 came out, but I still have all of my d6 books, and I'm toying around with the idea of converting the templates into classes.
Werewolf the Apocolypse - Great fun. Probably get back to playing this before too long.
1st Edition Dungeons and Dragons - Thinking of getting back into some of the older stuff, maybe run my friends through the Queen of the Spider super module.
Call of Cthulu - I actually got to play in this one, and had a blast. The guy who owns it hasn't run it in years, so I'm thinking of borrowing it from him and giving it a try.
Shadowrun - Just once, I'd like to be able to run this game. I've never really been able to get my friends into it. But I'll keep trying.
Marvel Super Heroes - Until I picked up M&M, this was our superhero game of choice. Good times.