The Twin Dilemma
The Gunfighters
Love and Monsters
Time and the Rani
Horror of Fang Rock
IMO, The Girl Who Waited is fantastic.
I don't think I've seen anyone hate Fang Rock before, I love it, but that's what's so great about Who, there really is something for everyone.
I haven't seen every Who story ever made (still in existance anyway) and even those I have seen with some it's been a while (so while I have seen The Twin Dilemma it's probably a good 15 years (at least) since I have so I can't in all concience put it in a bottom 5.
Classic Who wise I'd say Claws of Axos, The Leisure Hive, The Two Doctors (such a waste) Dragonfire and Ghostlight.
Nu Who; Fear Her, New Earth (notwithstanding the phenomanal bit where Cassandra dies in her own arms which almost redeems it) 42 (yawn inducing) Curse of the Black Spot and maybe last week.
Trouble is, especially in Nu Who, there's usually something to redeem most episodes, take last weeks, overall a bit meh yet still had a lump in my throat near the end
