When I was in seventh grade, the nun who taught our class religion would never get my name right. Every day, she'd abbreviate it, and I correct her.

This went on for about a month of so. Then one day, she get's my name wrong, and before I can open my mouth, the entire class (sans me), who were apparently as sick of it as I was, corrected her. At the top of their lungs.

(This was in a Catholic school. It didn't go over well, but she DID get my name right from then on.)