I'm going to be the first one to say, I'd want to be a fairy, they can do all sorts of cool things, like fly, cast magic (possible shape shifting), of course i'd still want to be a guy fairy. There are plenty of she fairies around my odds would be pretty good.
Or of course zora, something about how awesome they were potrayed in majora's mask really does it for me, with all the swimming and what not. They can live in all sorts of water, and on land, and people don't freak out when they see one.