The second rendition of 'Little Drummer Boy', surely one of the most revolting Christmas songs in history, was enough to make me leave one store emptyhanded. Carols sung badly by pop singers have the same effect - Mariah Carey, I'm looking at you.
'War is Over (Don't They Know It's Christmas)' does the same thing. If I find a radio station that plays that one, the the channel's quickly changed.
Go on, share your least-loved shopping and musical experiences.