Best double-zinger of VP debate

There are zingers, and then there is the rare double-zinger, where one debater scores a zing, and the opponent sends one right back.

Ryan:  (re Romney's "47%" comment:"I think the vice president very well knows that sometimes the words don't come out of your mouth the right way."

Biden: (without missing a beat): "But I always say what I mean."

Zing-Zing.

Ralph