Mine isn’t particularly advanced or cool but I built this little directory of kaomojis (text-based emoji) with a cat mascot while I was in San Francisco for an interview at Flickr (this was a long time ago). At the time I was a junior designer with very little dev experience, so this project helped get my feet wet.
I originally built it for a now-ex-girlfriend, but I use it all the time myself to add a little spice to things like tweets or error messages.