The French version of O Holy Night (Minuit Chrétien), for being featured at the end of the first Elvis Gratton movie, with a resurrected Elvis Gratton bursting out of his coffin as it is being carried away by pailbearers. One of the most awesome scenes in movie history.
Also, anything by Andy Williams. That guy can smarm like nobody's business.
Secular? Jingle Bells (or the French version, Vive le Vent; either is good).