A famous one and a personal one.
The famous one being between Lady Astor and Winston Churchill
Lady Astor said to Churchill, "If you were my husband, I'd poison your tea," to which he responded, "Madam, if you were my wife, I'd drink it!"
The Personal one was between myself and my wife, who will remain nameless. *grins*
The wife was telling me about a friend who will have some time off of work for the next few weeks.
Me: "How did she manage that?"
Wife: "She made a deal with a demon."
Me: "So...What did you get out of the deal?"
Wife: "What do you mean.... Hey!! Jerk."
Me: *Smirks, pleased as punch.*