My favorite coral is the one I don't have in my tank...
One of the most hardy is a Steve Tyree Limited Edition the "Idaho Grape". During the IMAS 2004 Reef Tour, Steve Tyree stopped by my house and talked me into trading a large frag of a montipora undata for one of his books. He sells one small frag a month for $75. I always wonder what he does with the rest. It is a nice coral that grows well and is very hardy. I am nearly convinced that this coral could be mass produced in a septic tank if a little salt was added and the lid left open...
Thanks,
Scott