It's been said a ton already, but IMO, the percula, or the ocellaris. Not just based upon looks, but also the way they move, and their personalities. Look up a couple of youtube videos of different types of clowns just swimming around, and in my opinion you'll fall for one of those two species every time. They way they bounce around when they swim just makes them look like all they are ever doing is goofing around and playing, and because of this, watching them always puts me in a better mood.