+2 on the YWG and the Randall's goby. Other possibilities are cleaner gobies (many are available captive-bred, sometimes even in pairs), tiger gobies (not the sand-sifting species, but the tiny striped ones that ORA breeds), and, as stated above, clown gobies (depending on your corals).
A lot of people who keep clown gobies have problems with them nipping at or irritating SPS, but I have a green one (G. atrangulatus) who's been a perfect citizen ever since I got him about six or seven months ago. (I suspect that part of this may be due to the fact that I don't have any acros.) He hops around and even sleeps in my branching montiporas all the time, and the corals are so used to him by now that they don't even retract their polyps anymore. Very colorful little fish, and very personable: every time I come up to the tank, he swims over to whichever side I'm on and perches in one of the SPS to stare right at me. He'll actually follow me all over the tank--probably hoping I'm about to feed him.