I have two that fit this category.
For games played at a convention, I have to go with Gregor Hutton's Best Friends. I have discussed it elsewhere and it is a crazy, silly game worth the price of admission.
For games played not at a convention, I have to go with Lowell Francis' Freakish Band of Adventurers campaign. The game was set in his 2nd continent fantasy setting using a homebrew system that was one part GURPs, one part BRP, one part RoleMaster with a heavy dose of Glorantha influence. The group was large, for me, 8 players at one point. I think I played the only straight human in the group. We had a half-demon, a cat person, a couple of elves, a dog person, a wizard of indeterminate heritage, and myself. The game was a disaster around every corner: we were constantly bumping into things, knocking plot points on their sides, releasing gods from imprisonment, and travelling to the moon to fight evil ratkin. We traversed the continent finding adventure and mayhem wherever we went. It ran for several years (3?) before being wrapped up. We lost a player due to him moving down to Indy at one point in the campaign.
I believe Lowell has some write ups on the game over at his blog, Age of Ravens.