OK, I had the idea for this, just bear with me.
Warriors of the Worlds
In each world, evil will rise. In each world, heroes will appear to try to vanquish that evil.
Now, the gods want to know which is the stronger. And they want a darn fine cross-section.
Drawing from each world(Greyhawk, FR, Dragonlance, any worlds we can think of from D&D or D20, really), heroes and villains find themselves drawn to dungeons by tales of powerful artifacts and treasures. Upon entering, they find a hideously deadly ordeal in place for them. Old enemies might set aside grudges for the sake of survival. And the worst is yet to come.
If they can survive their ways through these mazes, they will find a tunnel with a pinprick of light at the other end. If they follow the pinprick, they emerge...into sunlight. The gods have weeded out the losers, and now they want to find the ultimate winner, be they good or evil, Faerunian or Krynnish or Oerthling.
OK, so basically it's Game of Death, but with characters drawn from different worlds. If you want to include other books besides the 3 core books(such as Book of the Righteous and the Unholy Warrior's Handbook, for example) I could work on typing up a document featuring the OGC material for distribution via email. I think it'd be a really good game, provides plenty of opportunity for dungeon crawling AND roleplaying(although of course the second will be up to the individual DMs and players), and just in general sounds very much fun; you'd have tables grouped by world of origin during the dungeons, but then later on you'd have a free-for-all in a wild arena hosted by the gods themselves. I'd even volunteer to make a dungeon and DM. I'd also suggest making the starting characters somewhere between 10th and 12th level since they are supposed to be powerful heroes and villains.
It also helps out that in the beginning the tables don't have to stay in sync for the game to work properly, and by the time they reach the arena we could push some tables together and reform the groups for the free-for-all(since by then they'll have been through the meatgrinder's of the dungeon and probably be down a few people, ya know?).
So, wadaya think?
EDIT: Also, I can provide(if it's in hardcopy by then) free copies of my monster book for the other DMs, since I'm hoping to have it done and to the printers by next Gencon, I want to premiere it then.
P.P.S Yes I know it draws heavily on Game of Death; I really liked the idea behind GoD and thought it'd be godly to play like that live; the real innovation I added was that they're all from different established D&D worlds; maybe you could also have some of the gods subtly(or not so subtly) pushing for their world's heroes(or villains) to win? i.e., Lolth 'accidentally' leaves a powerful magic item in one of the dungeons that leads from the Forgotten Realms where she's sure a drow PC will find it, that sort of thing? It'd be another great RP idea. Another one I had was that as players fall, when the rest get to the arena of the gods, the fallen players can play and interact as various gods, figuring out what effects to bring down on the field each round, RPing amongst themselves, and things like that. A good way to keep people involved(although obviously the DMs, especially the head DM, would have final say in god effects).