Ten Episodes That Every Sci-Fi Show Must Have (if they last long enough) naturally includes quite a few that the Doctor has faced.
Christmas every year since 2005 (and that one time back in the day), alternate universes, important characters dying, flashbacks (which the characters can visit), time loops, betrayals and Blink.
Always room for more, though.
And what would you want in a Doctor Who Hallowe’en special? Hmm...