4. A Christmas Carol
This is possibly the first and definitely the last great Doctor Who Christmas Special. On Moffat's first go he managed to combine an epic tale with lovable, memorable characters and a truckload of Christmas spirit. On the basest, most immature level I love this episode because it is an entire era of Doctor Who in an hour, namely it's the Kazran and Abigail era. We see the Doctor meeting them, their first few adventures, dissent growing between The Doctor and his friends and finally the day when they must leave him. On the level of a pretentious literature student I see this as being a very rich script filled with easter eggs for the discerning fan willing to sit down with a notepad. There are themes of inspiration and finding understanding in the darkest of places, and it is the ultimate update of the Christmas Carol, replete with flying sharks. On the level of a hopelessly over-emotional, Christmas-loving fool it's just a mosh-pit of shmultz. I find the romance between Kazran and Abigail to be very compelling, and the tragic omnipresence of death makes theirs a bittersweet relationship. Yet the way Moffat simply mentions that, turning something as tragic as death into just another part of living just brings the whole script to a satisfying, poignant close.