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.
Favorite to hear once a year is The Little Drummer Boy. It does get old fast though. Silent Night is also up there.
Least favorite is Christmas Shoes and a lot of the real commercial pop ones. Also despite my love of the Beach Boys, I don't really like Little Saint Nick