O Come All Ye Faithful, particularly this arrangement by Celtic Woman (prepare to have your socks blown off OMG the harmonies!!)
The Christmas Shoes song makes me STABBY! Stabby, I say! Kid, Jesus ain’t gonna care what kinda shoes your mom is wearing when He takes her 'cross the River Jordan! Quit scamming!
The Carol of the Bells
I forgot about that one. 
I love so many it’s hard to pick. I always like Good King Wenceslas and other traditional songs.
also like the Brian Setzer Orchestra Getting In The Mood (for Christmas)
The other day I was blasted with I Saw Mommy Kissing Santa Claus at full volume in The Emporium shopping center. 
One song everyone knows over here is Jingle Bells, which the Thais always mangle to Jinger Ben when they sing it. But that makes it quite cute actually, a rousing chorus of “Jinger Ben, Jinger Ben …” etc. One long-time British expat journalist of my acquaintance alays refers to Christmas as Jinger Ben season.
anywhere that people go to shop is not the best place for music, just as a general rule.
I want to add I love the CD A Charlie Brown Christmas, not just for itself
but because it got me listening to Vince Guaraldi who is most awesome!
A belated entry:
Watched the film with my daughter the other night for the first time in years, and remembered just how much I love this song.
Enjoy! 
I love that song, and I love Celtic Woman, so I was prepared get my socks blown off. It did not disappoint. Thanks!