I'm cheating, because I'm not really about Christmas songs...I'm about Christmas music. Tied for first are the entire Vince Guaraldi composed soundtrack to A Charlie Brown Christmas, and Alfred Reed's Russian Christmas Music. Wall of sound at 11:45 - that's chills.
[video=youtube;axGZUcK70Xo]http://www.youtube.com/watch?v=axGZUcK70Xo[/video]