My favourites come in two flavours: ethereal, sparkling, mysterious Christmas magic (Carol of the Bells, December will be Magic, Walking in the Air), or the sort of thing that reminds me of dancing like a thing possessed at an infant school disco (Merry Xmas Everyone, I Wish it could be Christmas Everyday).
My least favourites are anything that might be included on a Daily Mail 'Crooners at Christmas' CD (of which my parents seem to have about 50), and anything at all by Micheal Buble, especially as my partner is a huge fan and has full control of what we listen to in the car.
However, they are nohting, nothing compared to the cynical, soulless, shitfest that is "Wonderful Dream (Holidays Are Coming)" sang by Melanie Thornton i.e.: the full length version of the Coca Cola ad song. I quite like the ad, but the single they made is actually genuinely sick -making with its faux-ernest lyrics about HOPE and PEACE and DREAMS (sample: "let the magic dry your tears and heal your heart" "now the children's eyes are shining, like they've never shone before, let their dreams and aspirations light our way, living life in harmony forever more"), in a song designed to flog crappy fizzy drinks. Spare me.