Im assuming you are talking about for you 10g. Damsels are very hardy fish, and most people use them to start up a new tank. However, with that small of a tank, you probably dont want more than 2 small fish total. Damsels can be very aggresive towards other fish, and are also a pain in the butt to get out.
A pair of clownfish would be a good choice IMO.
How long has your tank been running and whats in there right now?