Royal Gramma - I have always had one on my tanks. Firefish would be cool (helfrichi ones would be extra cool, if you have the cash!). Never had a Midas blenny, but watched one on youtube and looked like a way cool fish.
I'm going to get flamed for this, but I really like sixline wrasses. Having said that, many people comment that they are evil incarnate and will attack fish ten times their size when grown. Which is too bad . . .
In the spirit of the sohal tang, I'd say those baby leopard sharks they sell. How big can they get, really? Or a small Emperor angelfish with the col white scribbles on the blue background. ;-)