Like most people who have worked in retail/the service industry over the Christmas period, festive songs induce 'nam style flashbacks in me.
Especially Fairy Tale of New York.
I do like O Christmas Tree and Little Donkey from when we did the Nativity play when I was six years old. I was one of the Three Kings / Wise Men. My one and only time on stage. I started a fist fight with another King when the Jesus doll was being taken to the manger.