I love Trans Siberian Orchestra, especially their rendition of Carol of the bells.
TSO is great, but there is another good rendition of Carol of the Bells:
While CotB makes for a good entry in the category "magnificent", there are other great songs:
In the category of "Heartwarming": White Wine in the Sun by Tim Minchin
(Please excuse the rather prachy and political second verse)
And in the category of funny, Tom Lehrer's Christmas Carol