4. Bad Wolf/The Parting of the Ways (Story 166, 2005)
And then that was it. Just a handful of episodes and Eccleston was gone, replaced by some guy whose primary skill (at the time), seemed to be saying, Barcelona! in a slightly amusing fashion. This was a big, glorious story, that highlighted a lot of what was great about the Davies era. It showed the consequences faced by a companion when they leave their friends and family behind, played around a bit with time and showed us a Dalek army at the height of its power. This was also the show where future Torchwood star, Captain Jack (John Barrowman) became an immortal. Its also where Rose was possessed by the energy of the TARDIS and, yet again, the Doctor had to sacrifice himself to save a companion. It was a great pity that Eccleston left the show (through from the hints hes dropped over the years, I dont really blame him), but at least he went out with a bang.