An old-fashioned vanilla fantasy setting with humans only. No dwarves, no elves, no gnomes, no halflings, no demihumans.
One thing that has gotten me thinking about Game of Thrones is the lack of necessity for fantasy races. In my opinion all the stereotypes associated with fantasy races usually hinder roleplaying. I almost always know that if someone is creating a dwarf-character, there is a distinct possibility that it will not be an interesting character due to the stereotypes. And if you don't go along with the stereotypes, then it's going bother everybody/somebody.
Player: "My dwarf has a beard". Me: "Superb..."
Player: "My dwarf is beardless". Another player: "WHAT?!"
Ad infinitum...