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.
Fav: tie between "Have Yourself A Merry Little Christmas" and "Christmas Time is Here" from Peanuts.
Least: It's Cold Outside. Not because of sexism or anything but just because it's a bland song that people insist on fighting over.
Bonus: I actually like "All I Want For Christmas Is You". Sue me.