I'll start!

My first Pull Request that was ever merged was a set of translations for one of Francisco Franco's Android apps from English to Spanish, because that's my native language.

Although it wasn't a complicated task on it's own, I had no idea how Pull Requests, forks, and branches really worked back then and right after I got the email notification that it got merged I decided to learn Git more in depth by taking Udacity's Git related courses.

Needless to say, that was one of the best decisions I've ever made.