My favorite is "I Wish It Could Be Christmas Everyday", because my dad liked it and we always played it while decorating the tree when I was little. It brings back nice, happy childhood memories.
Least favorite by a mile is "Stay Another Day", which is a simp anthem disguised as a Christmas song, and then "All I Want For Christmas Is You" which is excruciating. Actually, I might overrule that and say I hate "Santa Baby" more, because it's just a gold digger begging for gifts.
If you want to torture yourself, here's the link. It was popular enough to be adapted into a movie.
It's not popular, but I enjoy this version of The Boar's Head Carol.