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.
Silent Night. My family sings it every Christmas Eve.
I don't hate songs, but I do hate renditions. Porky Pig singing Blue Christmas for example.