I'd like non-aggressive fish that all just get along so I'll go with (from very limited experience)...
Wish I hadn't but would probably stupidly do again:
-- Clownfish = menace,,, but you just gotta have 'em, right?
-- Male Bangaii cardinal = my current regret,,, but I'd never know how to find a female anyway,,, so,,, it is what it is (as they say)
Domino damsel, pearl damsel. Although, hands down the most aggressive one was a yellow damsel. I managed to catch him and put him in a tiny breeder box I was using as a mini refugium, where he tore the algae to shreds until I could return him to the LFS. Funny. I caught him easy, but could never catch the pearl damsel. The yellow damsel probably attacked the net.