Any mouse can be configured to work in left-handed mode (the buttons are switched around), but I can see that you would be horribly off-centre using WASD with your right hand.
I'm one of those left handers who has always gamed right-handed, but it's good to see that there are tools out there for those of us who have trouble. Now let's force everyone to learn Japanese and write from right to left so that THEY smudge the ink on the page