2. Silence in the Library/Forest of the Dead (Story 195, 2008)
Season four really was a good one for Doctor Who. Out of thirteen episodes aired in this season, six of them, spread out over four stories, are on this list. Not bad! Anyhow, this one has gone down in history for two catchphrases (Hey, who turned out the lights? and Donna Noble has left the Library. Donna Noble has been saved.), as well as for containing some terribly creepy monsters in the form of the Vashta Nerada. But whats really important here is that this story marks the end/beginning of the River Song saga. Yes, despite the fact that she is, for better or for worse, almost completely connected with the Eleventh Doctor, its important to remember that River Song got her start with the Tenth Doctor in this story, where shes killed off. Or is she? I wonder. Regardless, Alex Kingstons performance as River, combined with all the other goodness, makes this a truly great story and easily the best out of season four.