I've already cosplayed as Quasimodo from Disney's The Hunchback of Notre Dame. Not really a proper cosplay, though, so not sure if it counts. It was for a fancy dress pub crawl, the theme was Disney. If fancy dress counts then I've cosplayed as a German beer-guy, a modern-day Smurf and Zombie Michael Jackson before. Otherwise, never.
If I was into cosplay, then I'd try and spend some time and effort doing awesome costumes like that guy who made the Big Daddy suit, the Portal Gun and all sorts of other stuff. That would be pretty cool
