Thats a Mojano Anemone. Some keep em, some don't. Some get really good coloration in them. If you want to keep em, I'd seperate the rock its on from the rest, it will colonize this rock.
That's correct, a Majano. Some of them are very beautiful and some are florescent. They don't spread as fast as aiptasia, but most people treat them as pests.
Well after studying on the best way to get rid of him I tried the first couple of options... Prying him off (he just retracted into a hole), soaked him in hot water (couldn't get the whole rock under cause of the coral). So I finally just glued over all the holes on the bottom side of the rock.. We'll see if he pokes his little head out somewhere else tomorrow.