2. Vengeance on Varos (Story 138, 1985)
http://www.youtube.com/watch?v=LptcyA-zSnA This story is generally regarded as one of the darker ones of the original series. Its often derided for being very violent, which it is (though contrary to popular myth, the Doctor doesnt toss anyone into a pool of acid, but he is a dick when two people die in one). It is also a great episode, introducing the character of Sil, a great recurring villain who turned up twice in the original series and was supposed to show up a third time (
and eventually did in audio format). Plus you get Jason Connery, the son of the legendary Bond actor. The story also offers a surprisingly look at reality TV gone horribly wrong, and while it does present a glimpse into an unlikely situation, its still an interesting one. Its one of those great, mid-80s Doctor Who stories that shows what the show was really capable of when it tried, and its sad that more stories, especially those from the Sixth Doctor, do not live up to the standard here.