There was a Ramper who used to come up into the terminal and sing Christmas Carols over the gate PA system. He had a great voice and by the time he was done, everyone in the vicinity was totally focused on him.... he always got a standing ovation.

I can't sing, but I have been reading a little poem a co-worker wrote called "The Flight Before Christmas", once boarding is done as a way to get people to relax a bit. Really sets the mood for a nice flight. I think passengers appreciate something a bit out of the ordinary at times.