Any wrasse to be honest, anything except a SIX LINE. Most wrasses are free and open swimmers, and most are non aggressive towards any other fish except it's own kind.
While some are OK, once they mature every one is a murderous *******! Six line is probably one of the worst suggestions here, and I for one would never suggest a fish that not only can, but will murder everything your tank.
For those suggesting a clown goby, she said she wanted an acgtive fish, not a coral croucher! I've had many of them over the years, and not a single one ever openly swam, except during feeding time. They are called coral crouchers for a reason. lol