For me it's Romney's "You've got to be kidding..." line.
I also liked Huckabee's "I don't know what school you went to..." and Gilmore's "It's not about Karl Rove..."
speaking about quotes...Duncan Hunter’s “I’m talking about a real fence not the flimsy one CNN shows with people climbing over it.”
Personally, I like Hunter’s “Precise targeting of ordinances” or whatever it was, about what the government has done well.