Working together with @itsdavidhughes, @xz & @jonathan1707, we created a web app for the Euro 2012 competition called Guessi.
Players of the game are presented with that day's upcoming matches, they submit their choice for who will win and if they guess right then they gain points and advance in the league.
This was a lot of fun to work on, and made the whole competition more interesting, especially seeing hundreds of people playing with a little app you made just for fun. Hope to work on more things like this in the future.