A while back at My Play, Gerald Cameron proposed the idea of the "BHAC" (Big, Hairy, Audacious Campaign), the sort of campaign that's earth-trembling huge its shear audacity and (I'm assuming) its variance from the norm.
He throws out one example: normal D&D campaigns usually have a home town or city ... what happens if that city is build on the corpse of a tarrasque? It spawned a corresponding conversation over at Treasure Tables, with examples like a world overrun by vampires, a world in which everyone has superpowers, and one where giants rule over millions of humanoid slaves.
