About four years ago I took my son to one of the vinyl-free carboots here.
A German seller with a ridiculous Kaiser Wilhelm tache had a battered mandolin on the floor in front of his stall with a ridiculous price tag on it. While I was looking through some books nearby, my lad,who was five, decided to strum the strings of the mandolin gently.
Suddenly the owner screamed "FINGERN AUF!!! in his face,which understandably sent him off into floods of tears.
About five seconds later I had the guy by the jacket and had barged over half his store before his missus and other sellers intervened. He was cursing me in German, and pointing to a sign that said Nicht anfassen, so I told him in his own language that he should try using the language of the country he was in. I regret to say I also threw in some Nazi comments, too.
Please add your own carboot scuffles, chazza pagga or fleamarket fisticuffs.