What's the smallest thing a stranger did for you that you still remember?

I'm not talking about life-saving heroics or grand gestures. I mean the sort of thing you'd forget within a week if you were a normal person, but for some reason it stuck. Maybe someone held a door a little too long, or a kid waved at you on the bus. I've got a few from my mail route days, and I'm wondering if I'm the only one who hoards these little moments.