I made a PR to AngularJS that was quite large, adding handling for HTML5 date-time inputs. When it was merged by Tobias Bosch it ended up getting merged under his name, which was a little disappointing at the time (because I wanted that sweet github street cred), but I was still thrilled my contribution made it in. Again, very educational around the processes, etc. with regards to contributing to open source. It was a great experience.