Not that good of a game, though. A shame, too. Steve Jackson has put out some pretty good stuff, but also 20,000 versions of Munchkin because it sells.
Also, there's Pathfinder Munchkin. Considering that standard Munchkin is a parody of Dungeons and Dragons and Pathfinder is more or less literally D&D 3.75, I'm not entirely sure how that works.