Recently our group ran a short campaign (four episodes) of
All Flesh Must Be Eaten -- this is fun for character generation and for a session or two, but gets repetitive very quickly unless the GM is really on his toes.
Before that we ran
Ars Magica for about a year -- I love this game! And if you poke around, you can still find the 4th edition of the rules free as a pdf on the Net, such as here:
http://e23.sjgames.com/item.html?id=AG0204
Our next game up is going to be an old setting of mine, New Mavarga, retooled using a variant of the
7th Sea rules -- the rules are great for swashbuckling, but I loathe the world of Theah, so this is a near-perfect match!
Over 30 years of gaming, I have played under at least a dozen of rules sets --
OD&D, Metamorphosis Alpha, Empire of the Petal Throne, The Fantasty Trip, Chivalry & Sorcery, Traveller, RuneQuest, AD&D, GURPS, Champions, Harnmaster, Golden Heroes, FASA Star Trek, World of Darkness (old version, mainly
Mage),
Paranoia (various versions), Pendragon,
Cyberpunk (and
Cyberpunk 2.0.2.0),
Over the Edge, Ars Magica (2nd-5th editions),
D&D 3e, Burning Wheel, and the abovementioned game... I have no system loyalty and constantly look for the rules that best match the setting, rather than forcing a setting to conform to the rules at hand.