This sign gets me every time. EVERY TIME.
Fairy Fountain (Death Mountain Crater)
Like I said, the world's not totally completed yet, and there are no NPCs, items, and so on, AND I spent only about ten minutes exploring it tonight, but it's definitely still worth checking out, especially if you're a fan of the game (either one, I guess). There's just something about walking around a Hyrule that looks like it's made out of Legos...