Just fixing a build error, but anyway it made me proud at the time.
Years ago I acquired a TV-Tuner. When I bought it I was aware that both is wasn’t working in Linux and a driver was being written for it.
Having not enough knowledge and free time for anything besides testing the driver, and needing the device working, I began to pull, compile and see-if-it-works in a daily basis. One day the building was failing, I fixed it and submitted the patch and the patch got merged by the maintainer. Two years later it entered mainline.
At the end I couldn’t get the device fully working and gave it to a friend who had a supported OS so all I’ve left from that tuner was another fun experience of contributing to free software.