I was about 12 when I attended a craft fayre with a school friend and no adults. I stood by one stall of polished stones with my friend, and we went through little gifts we had brought for our parents and siblings. I had nothing for my mum, and only about 30p left, and was in despair about finding something nice, when the man behind the stall handed me a green polished stone, and said, "This is free, and I think your mum would like this" - and she did!
I still remember his kindness, 45 years later.
Anyone else?