Ben Folds at the National.

Upon first entering the building, there was a table with blank paper and pens next to a sign that read:

Write down your song request.
Make it in to a paper airplane.
Please hold your airplane until
you are told to launch to the stage.
Thank you

When Ben Folds walked out on stage he asked everyone to fly their song requests to the stage. Then he would pick a plane and play the song. I am not that familiar his music, but I thought this was an awesome idea. He put on a fun show.