The three halichoeres wrasses halichoeres ornatissimus (Ornate/Christmas Wrasse), halichoeres chrysus (Yellow/Canary/Yellow Coris Wrasse) and halichoeres iridis (Radiant Wrasse) are the three halichoeres wrasses Robert Fenner most highly recommends because they're relatively small, hardy and generally peaceful (except with conspecifics). The Canary Wrasse can actually live in groups, so long as everyone's introduced together.
These three wrasses tend to be peaceful with fish and uninterested in coral. They do eat small crustaceans, though. They do a great job, in general, of eating nuisance inverts (flatworms etc) but may also decide to munch the snails, hermits or shrimp you actually bought and paid for.