I like the sun too much to be a vampire. They're almost always pale motherfuckers. Plus the stake through the heart sucks balls too.
There are a lot of mythical creatures, but, inevitably, they all have some weakness. It would be fun to be a centaur, I suppose - running seriously fast over long distances, having people ride you , having an awesome mane and sleek coat... But there's the problem of jumping directly up, moving backwards, going down stairs etc.
Dragons are frikking awesome. Not only are you insanely intelligent, but you get to hoard loads of treasure for no reason other than you like the shinyness of it. Plus YOU CAN FLY! And BREATHE FIRE! And because you're coldblooded, you'd have to sunbathe a few hours a day to keep yourself in working order. The downside is the bastards trying to kill you all the time to make a name for themselves, or steal your treasure etc.
Aqrabuamelu are cool. I suppose the best of both worlds would be a male
Campe (dragon/man/scorpion).