My vote is for a royal gramma. Bright purple and yellow, and pretty bold once established.
I also love the McCosker's and Carpenter's wrasses (and really all flasher wrasses). I have a Carpenter's now and would love to add another (more) to my 75. All the literature says one male per tank, but I've never seen how to sex them. They are jumpers, so a canopy, screen, or cover is a must with these guys.
I order all my fish online (becasue I can't afford the prices at the LFS
). A gramma will run around $15 (sometimes as low as $10 on sale) and you can catch the Carpenter's or McCosker's wrasses on sale around $30 if you are patient.