I like fish that have a function in my reef and just few others for added interest.
Workers:
Purple or Dejardini Tangs- Dejardinis will eat algaes that no other fish will
Some type of algae eating blenny - Golden, ember, sailfin
Nudibranch eating wrasse - Xmas, yellow coris, pink stripe, etc.
or
Four-lined wrasse
For looks:
Anthias*- Bartletts because they are pretty and easy to keep
Pseudochromis or Basslet - orchid, sunset, elegant, royal gramma, black-cap
Flasher wrasses*
Clownfish - only if I have an anemone. For me the relationship between a clown and its anemone is so cool that there is just this weird void if you have one without the other.
*need a net cover if you have anthias and/or flasher wrasses