The upcoming Pathfinder game has rekindled my love of the developed setting for the game -- Golarion. I bought the Gazetteer ages ago and dug it out for last night's character creation session. It's marvelous; I don't think I've really liked a published setting this much since I bought the Forgotten Realms grey box in 9th grade.
The setting is such a glorious pastiche of history, fantasy tropes, and gaming homages. Anything and everything is there -- decadent devil empires (Cheliax), pirate fleets (The Shackles and the Hurricane King), Norse-ish Barbarians (Lands of the Linnorm Kings), and tons of other stuff (gothic horror, proto-democracy, pharaohs, ape-kings, etc). Listing it like that, it almost looks silly. There's no way all this can be crammed into one game setting and not result in a terrible, terrible mess.
But it all works! At least for me. Adventure possibilities leap off of every page of the Gazetteer, as does potential socio-political conflict (if one chooses to include that in a game). As sketched out, Golarion can accommodate almost every conceivable character background, drive for adventure, and adventure setting.
I know there are 478 published supplements that further detail areas of Golarion, including a larger hardback overview of the entire world, but I'm going to try and resist them. The Gazetteer is just so fun!
Plus "Gazetteer" is a cool word in and of itself.