My characters are often the really shy, crazy smart ones. I find it easier to play them, because I find it easy to write characters who analyze situations the way I would.
Currently, I'm on a bit of a [url=http://tvtropes.org/pmwiki/pmwiki.php/Main/BrokenBird]Broken Bird [/url] kick, in that almost all of my characters suddenly have REALLY dark, gory backstories. I don't know why. O.o