yellow-tailed blue damsel for the cute category. Not everybody's fav because having to move everything around to catch a $4 fish is no fun, but I just love the personality and perkiness. Always has that look like it is planning something suspicous.
Most beautiful would have to be the lion. Haven't had one yet (wife gives me a dirty look when I mention one for her clown tank), but I think they're gorgeous.
Ok then, any species of arowanna gets my vote, but from what I can hope to have any time soon, citron goby or a mandrin (although the later may still be out of my reach).
Mine would have to be a Clown Trigger or a Ribbon Eel. Clown Trigger would win out due to their personality etc, but Ribbon Eels are so cool too and can hardly wait to graduate college in Dec so can finally get some again!.