I was involved in this competition, although I got accepted to interview with them, I wasn't accepted for the summer.

I got sidetracked with a fairly crazy idea and went out on a whim. I should have done something closer to my own expertise, and didn't build a prototype. Very difficult to pitch without a prototype.

My actual interview was a disaster. I had 3 backups of the PowerPoint, but they were all old copies (LOL). I had to give the presentation from Contingency Plan #4, hand-outs ;)