Would MeFites be interested in a MetaFilter RPG community on Google+ (or some other forum if you have it)? [more inside]
How about a MetaFilter Dungeons and Dragons (and other RPGs, of course) club/forum? [more inside]
D&D (or related RPG) mefites in Philadelphia area? [more inside]
This is my greatest stolen modified idea today. Metafilter hitpoints! We all get 5000 to start. Once you level up via unattacked thread posting, you can cast healing spells on your favorite, but inexplicably hated MeFi pals, or do double damage with Fireballs. Anybody who reaches zero has their account closed, unless someone ells resurrects you by sacrificing 3/4 of their remaining points.