This is the other special that made the list. This is one of those nearly flawless episodes that works on almost every level. It does a great job of building tension, introduces us to several wonderful supporting characters that we actually get to know a bit before their horrible deaths, and has some wonderful production values to it. But the real payoff here, at least as far as Im concerned, is the final scene where we get to see just how thin the dividing line between the Doctor and the Master actually is. The bits where the Doctor is gloating about how hes now the one true lord of time are truly chilling and Tennant does a great job here.