Oh wow. Well I'd definitely be taller. I'm 5 foot 1, and that just sucks. If I could, I'd be at least 6 foot. I'd have a muscly upper body. I'm working at it at the moment, but given biology, it's unlikely to ever get where I want it to be. I wouldn't have any scars. My hands and feet would be bigger (I'm a woman's size 3 and a half in shoes). And then the obvious stuff. I'd be an outie down there and I'd have a flat chest.
If I could, I'd change pretty much everything about myself. Except maybe not my eyes. I think I quite like my eyes.