3. The Stolen Earth/Journey's End
The final regular series episode to feature David Tennant, the return of Davros and the Daleks, and the meeting of all the major companions to have entered the series since 2005, the Stolen Earth and Journey's End provided a menacing, fast-paced conclusion to the normal run of the Tenth Doctor, and saying goodbye to the majority of the Time Lord's traveling companions. When the Earth is stolen by the Daleks to create the ultimate weapon, a reality bomb, the Doctor has to locate the planet, find out his foes and ultimately stop them. Throw in an unexpected regeneration, plot twists and cliffhangers, it almost edges the previous entry in my memory. In fact, the regeneration is my favorite part of the whole two parter. It is why shows like this are remembered - plot twists which stick in the viewers mind, make them talk about it for days and hours, and make them relish the next episode even more than before. The inclusion of so many companions makes it difficult to focus solely on one character, yet the abundance of appearances and the satisfying episode conclusion make it a fitting send-off for the Tenth Doctor. The appearance of Davros as well adds to the menace of the Daleks, and the survival of the very race is called into question - it's almost perfect Who