Girl or boy?
I personally prefer the boy theory, because the thought of a super-fabulous dragon who likes to dress up as little girls makes me laugh. Either way though, s/he is still my favourite WoW character.
(Interestingly, when I made this same thread on the blizzard forums, it got insta-deleted while the thread about whether or not Arthas poops went on for about 30 pages. Gotta love that homophobia.)