I'd have to vote for Cam Newton. He took a 7-9 team and turned them into a 13(14?)-0 team. The Panthers are not just winning, but blowing teams out.
My 2nd place vote would got to Tom Brady. It's great that he can win with no running game to speak of and a injury depleted receiving corp. I expect this of him, that's why I give the nod to Cam.