I love a good, snappy comeback.
In one of the bookstores recently I observed two coworkers who were not working together very well. The younger fellow seemed to be thwarting the more mature woman at every turn, although it was clearly unintentional. At one point he tried to help her stack books on an end cap and somehow managed to spill books across an entire aisle. Trembling with frustration she said, "You were sent here by the devil himself just to destroy me, weren't you?"
To which, the young man replied, "Well, yes, I am an agent of Satan... but my duties are largely ceremonial."