As I consider what sports would suit my daughter, I have to take her size into account.
She's her mother's daughter. She's a wee, puny thing--always the smallest in her class, and fragile-boned like a bird. She can play sports like soccer while she's young, but she won't be able to do as well at them when she's older, and brawny brutes begin to dominate the field. Trust me, I'm speaking from experience.
Dance is a good choice, because it isn't size-dependent. (I know, it's not really a sport, but at least it's exercise!)
Archery has already attracted her interest, thanks to the archers at the Celtic Festival. We'll look into archery when she's big enough to handle a bow.
Horseback riding is another one in which you can be small and still succeed.
Any other ideas? Keep in mind that she likes to win. The sport most likely to hold her interest will be one in which she can do well despite her size and relative lack of strength.