10. Reuniting With River In "The Time Of Angels"
In addition to a brand new Doctor, series 5 had another delightful treat for fans in the form of River Song's return. The Doctor first met the enigmatic time-traveling archaeologist in Silence In the Library, and her knowledge of the Doctor's future hinted at some fascinating adventures.
The Doctor always knew he was going to see her again one day--he just wasn't expecting it to be on a crashing spaceship carrying a Weeping Angel.