Guitar World usually puts out a Christmas tab booklet with a few songs in it. UG has a few good tabs for Ode to Joy....
Try Steve Ouimettes We Three Kings if you can find tab (good luck) that song shreds some ass.
Ode to Joy is your best bet, but maybe try:
Auld Lang Syne
Jingle Bell Rock
Hark! The Herald Angels Sing
The First Noel
Jingle Bells
Deck The Hall
Silent Night ( really freaking easy)
Oh Come All Ye Faithfull