Unsolicited generosity
Stopped at an ATM to get cash, the machine did everything including give me a receipt for a withdrawal but failed to dispense any money. Long story short, another customer overheard what had happened and under a misunderstanding that it was all the money I had left, offered me 20 bucks for gas money to get home. I was momentarily shocked, but I explained I didn't need it, but it was a very generous thing to do, and that I would still pay it forward if he would save it for someone who actually needed it. I shook his hands and we parted ways.