Someone I don't really know all that well, last spoke at school, has an autistic niece. She lost her toy and was distraught, so her aunt put up a post on Facebook to say it was discontinued, and to ask if someone could locate a second hand one somewhere. I'm not really sure why, but I felt bad for her and thought that maybe I'll use my Google-fu to help.
I did a reverse image lookup, found the original manufacturer, looked up one of the main execs, found their contact details against their personal domain, and asked them if they could help out. They said they'd be happy to help, and I said as a gesture of good will that I'd pay for the new toy - perhaps several so that she'll always have one if it were to break.
After speaking to the owner, I had paid for several toys for an autistic girl I had never met - probably around £500 worth. The exec went a step further and flew to the UK to give her and her aunt the toys, probably for some good press. I never told the aunt it was me, and I told the exec to keep it between us. They put out a press release where I was referred to as a "mystery hero", and said that for her they would resume that line of toys, with her receiving a custom version with her name attached. To their credit, he said her aunt and mother kept asking who the person was so they could thank me, but they stayed firm and said that it was up to me to reveal myself.
So, for £500 I made an autistic girl and her family happy, and got a nice photo of the workers with a note that said "thank you". That money was supposed to go towards car repairs, but I decided that a month of walking and leftovers for lunch to make someone happy was worth it.