Many years ago, I was with some fellow volunteers outside a popular shopping mall, raising money for a new ambulance. There were many people who could have obviously been able to spare a bill or two, but they were too full of themselves to even look at our faces, let alone the fliers we were handing out.
Then one old guy with a bottle of beer in one hand and dressed like that was his only dinner came out of the shop, looked at us, and put his beer change in our bucket, saying something along the lines of "you do something important".
Made our day.