I voted for Christmastime is Here. Back when I could remember the first couple of chords, I would sit down at a piano (somewhere in public) and play the familiar song. That would get everyone's attention and everyone would smile and come over to the piano. Then I would drift off and say, "Sorry, I only know the first few chords." I did the same thing with a guitar and Stairway to Heaven in Japan and got a very polite round of applause after trailing off about eight chords in.
My favorite Christmas recording is of a December 25th, 1971 Modern Jazz Quartet concert, with guest Paul Desmond. They open with a nice Greensleeves waltz, play a couple of standards, then do a funky, psuedo-sleighbell-driven Jesus Christ Superstar. The recording is on the Red Baron label and is truely one of Paul Desmond's finest moments (so much so, that John Lewis fought for years to have it released).