Over hosting - people constantly trying to feed you, insisting you take biscuits etc when I don't bloody want one
I was offered some malt loaf (which I can't stand) once at friends, so I said, no thank you. Next thing I was given a plate with a huge slice on. I was stuck with this cake that I can't stand, didn't want and had already said no to... If manners is meant to make people feel comfortable, that was the exact opposite!
I left the cake on a side table in the end!