Just once. Well, maybe not just once. There's something I consider a half.
She was a friend I recently met in class, and we played Maplestory with each other for a while. It resulted in her MSNing me up and saying "emIthinkIlikeyouwouldyougooutwithme". I ended up saying no because I know she's just bicurious and not serious + not compatible.
The half was just a guy who said "Would you be more girly if I asked you out?", to which I said no, and he said nevermind.
I've asked several people out, though.
Only one said yes. We dated for about 9 months.
Most of the others were straight. Instant rejection, asked nevertheless. xD