My favorite Christmas Specials have always, all the way back to my earliest memories, been the Rankin/Bass "Little Drummer Boy" and adaptations of Charles Dickens' "A Christmas Carol."
My particular favorites out of the 'Christmas Carol' bunch are "A Muppet Christmas Carol", starring Michael Cain as Scrooge. It only Muppet movie that ever managed to be truly and honestly heart-jerking and tear-invoking. The other being "Mickey's Christmas Carol", a 1983 animated Disney adaptation featuring Scrooge McDuck as Mr. Scrooge.
And, I just absolutely adore Rankin and Bass's "The Little Drummer Boy".