The nominees for favorite snappy repartee are:
From "Love and Death"
Bert: "How old is she?" Nick: "Let's just say somewhere between Baby Boomer and Jurassic."

From "Reborn"
Nick: "Assume the position!" Amanda:"Well, I usually get dinner first."

From "Immunity"
Nick: "Eternity is overrated." Amanda:"You're telling ME!"

From "Thick as Thieves"
Amanda: "... I want to buy you a cappuccino." Dexter:"with chocolate on top?"

From "A Matter of Time"
Amanda: "Holy ground, Korda." Korda:"Ever heard of foreplay?

and the winner is.....