White Christmas from Bing could be a little obvious but I remember Little Donkey as my Mum, Dad and younger Brother sat round eating our Christmas dinner in 1959. Not ashamed for the age of all this.
'Stop the Cavalry' by Jona Lewie is always a welcome break from the Wham/Pogues/Slade/Wizzard bombardment. Frankie's 'Power of Love' takes me back to the day, as does St Etienne's 'I was born on Christmas Day'.
Christmas Wrapping is a good one, and not heard often enough!
I know it's not technically a Christmas song, but Jingle Bells by Fats Waller always makes me cheerful. And Eartha Kitt's Santa Baby must be the sexiest Christmas song around!
And, for the kids, I don't think you can beat Where did my snowman go? by Petula Clark, backed by a chorus of Barnardo's kids back in the 1950s (again, not technically Christmas, but always goes down well at this time of year).