I have always played as a male in games. In WoW, SWG, PS and all other onlines games. I don't know why but just like Tybo I feel uncomfortable using a girl avatar. I small part of that is because I know how guys act so different in game around girls. TRxShade would be on TS and not speak and everyone would be themselves but as soon as she spoke everyone that didn't know her would go silent and be like 'girl, girl, girl' and start acting dumb.
I have made one PS character that was a female, TopDawg and I made them on VS Werner just to use that one annoying voice and run around taunting everything as we killed them. Those chars are BR3 and BR4 I think.
As for chicks playing games, go for it I could give a sh*t less who/what you are you are just a notch on my kill column ;).