HipPriestFavourite 4th Doctor Story
Obviously this question is going to be asked at some point so I might as well be the obvious one and ask it......
ᴇᴍᴘᴇʀᴏʀ 帝The Brain of Morbius - still freaks me out to this day. Went to the Dr Who exhibition and there it is in a glass cabinet, staring at me malevolently.