Jingle Bells Rock is one of my favourite ones. I like also Have Yourself a Merry Little Christmas(?) and Sleigh Ride. There are also some domestic that I like even if them aren't truly my favourites. Sylvia's Christmas Song is very beautiful and The Sparrow on Christmas Morning too.
There's a Finnish version about The Sparrow on Cristmas Morning if you want to hear:
And Sylvia's Christmas Song. It's lyrics has been also translated in English but I don't know if anybody has sung it in English