>>6090984Although I'm not sure if it's confirmed by anything, he was probably ambidextrous because even with his left arm broken, he fights rather well with his right in Oolacile. Also, other than the box art (which I don't recall ever officially being named Artorias, but at the same time it wouldn't be too far fetched for that to have been him) he's never shown being either left or right dominant.
Despite all the lack of proof, I would like to think of Artorias being left-handed, and all those other unconfirmed little things.