Milk chocolate
It's like being involved with a serial philanderer. You find out that he had sex with your sister -- in your bed -- and you live and let live, so as to not rock the boat. Then you find out about the secret love child he had with his secretary, and you take it and hope that your kids will like their new half-sibling. Then he gambles away your life's savings and puts you in debt, and you let him slide with a promise to never do it again.

Than comes Valentine's Day... and he gives you a box of milk chocolate when he knows damn well that you love dark chocolate and can't stand milk chocolate. How dare he! All hell breaks loose: "You don't have to yell." "I will yell!" And you finally kick him and his milk chocolates out of the house.