Or...want to turn the other cheek with a bit of sass?
Co-worker (at 5pm): Hey, can you finish this project for the 8am meeting for me? I have an appointment for a French manicure that I just can't miss.
You, biblically versed: Harken, O thou breaker of the commandments, for you will be taunted by the king's concubines!
Family member: You know, I think that pie you brought to the Thanksgiving dinner gave me food poisoning. Again.
You, biblically versed: O ye wayward winebibber...you will be plagued with gnats, flies and locusts!
Annoying anonymous shopper: Geez, how many kids do you have? And can't you keep them quiet?
You, biblically versed: Behold, thou shalt become as popular as a boil on the king's backside, thou offspring of a squashed cockroach!
(Hat tip to Fanatholic for the Ship O' Fools Biblical Curse generator.)
UPDATE: Feeling Shakespearean rather than Biblical?
Someone cuts you off in traffic, you could roll down your window and shout:
Thou infectious rude-growing horn-beast!
Thou errant toad-spotted dewberry!
Thou spleeny rude-growing incontinent varlet!