I really like my Pocillopora damicornis. A lot of the frags you seen in stores are greenish-brown, but Dr. Mac carries some very colorful aquacultured frags (bright pink, yellow w/green polyps). And they're hardy: my yellow damicornis was picked almost bare by an underfed shrimp, and it's already grown almost all of its polyps back just 10 days later or so.