Rondo has been immensely impressive, and so, too, has Pierce, but when you factor in the players he has shutdown, in addition to his own contributions on the boards and in putting the ball in the hoop, I'd definitely have to say KG.
Multiple players on this team are vitally important, but if there had to be an MVP, it would probably have to be KG. Then again, Pierce is very deserving as well. Pierce has had some truly monstrous games for us against some tough opponents as well.
You know what? I'd give it to KG.