In Nativitatem Domini Canticum H. 416 by Marc-Antoine Charpentier performed by William Christie and Les Arts Florissants.
That's H. 416 recorded on Erato in 2000, not H. 414 of similar title recorded by the same forces on Harmonia Mundi in 1982, also essential. Both the composition and performance have such an ease and inevitability, you feel you could just sit write down and write it like you might make a grocery list, or get up and sing it like you sing “Roxanne” in the shower. Like the best Christmas music, it acknowledges the need for salvation before the arrival of salvation (see also Honnegger's Christmas Cantata).
Run Rudolph Run by Keith Richards
Wicked Id at the Armadillo in '94, man!
For those of you who may have somehow missed that performance (in which I spontaneously conducted a break with a no-look, Paul Shaffer-esque wave of my arm before the final “reeling like a merry-go-round” that I was surprised the band actually followed as much as they were surprised to actually play it), we have the somewhat more famous Keith Richards 1978 recording of Chuck Berry's Christmas ditty. I particularly like they way the bass part maintains that same rhythm (and-4-and-1) for the whole song.