Gee, I'd have to post a good 2 dozen pix or so (and believe me, we have TONS of nice pix) because all of our fish have their own qualities, however, maybe i can narrow it down a bit:
"WOW" factor:
Rhinopias frondosa (weedy scorpionfish)

Pterois volitans

"weird factor"
Corydactylus multibarbus (bearded ghoul)

Inimicus japonicus (pop-eyed sea goblin)

Rare factor:
Parapterois heturura (bluefin/blackfoot lionfish)

Oxymonacanthus longirostris (Orange-spotted filefish)

Of course, there's "cute factor" too, and whatever else, but you get the idea...