I remember being forced to download Github freshman fall. Now that I'm graduating, I can look back fondly on the times I committed trash code to master, tried undoing my mistake, and deleting all of my code accidentally (and sometimes permanently). I digress. I've worked on several teams that went from a single (heavily workshopped) idea to a fully functional website or app. My favorites were Notable and Momento.
Freshman year -- The goal for Notable was to build a fully accessible note taking app that could automatically format text by importance , i.e. figuring out what the topic was and formatting text to fit underneath it.
Sophomore or Junior year -- Momento was about building and preserving meaningful connections via a shared timeline. We'd notify users (we imagined significant others) randomly about some nice time they'd have together. It's human nature to only remember negative things that happen to us so we really wanted to try working against that. Long story short -- a couple got engaged while using our app! They posted pictures on their timeline :-)
React native baby!