This popped up on Twitter the other day:
I replied with a list. Then remembered a few more. Then another few more. Then some more, then I gave up and decided to post the list here instead. I knew I'd played more than four. I didn't realise it had been more than ten times that.
This list doesn't include the games I've owned and never played -- which is a smaller list, but only just! -- nor the games for which I've generated characters and then the game never happened.
Adventures in Middle Earth
Barbarians of Lemuria
Call of Cthulhu
Dragonlance: The Fifth Age
Dungeons and Dragons (Basic, 2, 4, and 5)
Lamentations of the Flame Princess
Legend of the Five Rings
Middle Earth Roleplaying
Mutant (Year Zero, Genlab Alpha, Mechatron)
The One Ring
Phoenix: Dawn Command
Red Box Hack
A Song of Ice and Fire (sort of; Ben used the rules to run an Arthurian game)
Star Wars (d6)
Trail of Cthulhu
Traveller: The New Era
Vampire: The Masquerade
Warhammer Fantasy Roleplay
I think that's it, but I expect to remember half a dozen more games about thirty seconds after I click "Publish".