Most of the winners at the one I judged stood out.
One team was doing my "Procedural generation challenge" and managed to generate a playable underwater game in 24 hours, looked lovely.
Another team created a crappy game, but developed a system that let you just dump smart phones and tablets on a table and link them to form one display. In any orientation, cool code.
Others just created a port of any old 8 bit game, not really impressive.
Another hacked a xbox kinect box to work on a PC and wrote a simple motion input game
The last one I remember did an augmented reality game, wasn't very playable, but looked very cool.