Sleepy, if you do a search here for "@ Christmas" or "@Christmas Song" I think you'll find a number of threads that suggest quite a few not-so-common Christmas season songs.

Some of the songs suggested (many with links or with lyrics and chords) are silly and/or irreverent, many are serious.   

I can make a few suggestions but I'm strapped for time right now, but the ones I'd suggest are all in those other threads (e.g., the thread titled "Know any Hard-hitting Christmas songs?").

G