Write with my right hand exclusively but I'll flip flop on a number of other things: what hand I hold the phone with, drink with, eat with, hold the remote in, play tennis with er well badminton anyways; tennis is generally both; etc. Then there are random things like typing using only my left hand which acts like a dancing spider. Maybe I should just buy a tarantula and teach it to break dance and river dance; it'll make writing papers go much faster and I'll get to spend that time playing on the x-box.
Voted ambidextrous since writing is the only thing I can't do left-handed pretty much.