Pentax 6x7, because I own one, and it gets attention (the wooden handgrip is a nice added touch). But my own personal favorite in the would-love-to-have-it-for-the-looks department? Rolleiflex SL66. (Not that I can afford one, or if I could, would be able to justify it.)
Folders are also neat to walk around with, and unfold theatrically--I have a Balda Baldax that makes quite an impression and is fun to shoot with (and is much less obtrusive than the Pentax).