I think my favorite is "Carol of the Bells".
I love pretty much all traditional Christmas carols. Silent Night, O Holy Night, Adeste Fideles, you name it.
Also, I recently had the opportunity to sing in the choir in a performance of Handel's
Messiah, so I'm going to add "For Unto Us A Child Is Born" to the list. It's a PITA to sing, with those long runs on the word "born" - but it sounds so awesome.
