I would have to say the Naso or Powder Blue. My friend's naso lets him 'pet' him- very personable fish. I had a Powder Blue and he was really fun to watch- active to the point of being a bit crazy in my opinion. He hung out with my yellow tang and angel fish and 'played' with my chromis.
I just bought a Convict Tang last week. The little guy seems to be doing well and is supposedly one of the most peaceful tangs. I'll have to get a picture up.
Still wish I had the room to house a naso though. They have 2 large ones in my LFS in a tank with a Sohal Tang. I never really admired the Sohals until I saw that one. He surfs the water current all the time there. Wish I had enough room for one of those too.