Built Video Hub App that almost 5,000 people have purchased. I was a math teacher, became a web dev 6 years ago, built this 5 years ago. Most proceeds go to charity. Very minor by comparison to others, but I'm just starting out ;)

https://videohubapp.com/ && https://github.com/whyboris/Video-Hub-App

What I did that is most impactful is that I've been giving at least 10% of my income to cost-effective charities for over 10 years now (see Giving What We Can - thousands of others do the same). This amounts to almost $100,000 given to charity which translates to thousands of people protected from malaria for many years of their lives.