Yellow headed jawfish. Extremely under rated, very affordable if you buy diver direct from Florida, like living in colonies, and amazing personalities. Excellent tankmates for seahorses! I have a trio in with my ponies and pipefish, and they are just such awesome little fish.
On a similar note, I think butterflies are completely underrated. So many people avoid them because they may eat coral, but most are probably safe with the majority of corals. They usually only eat one or two species, not everything under the sun, and with some experimentation and removal of whatever corals they like, may be a perfect fish for a lot of people. Again, they may eat certain corals, they may eat all the corals, or none at all, just have to experiment and see.