I can't name my least favourite books, since when I immensely dislike a book I stop reading it and pretty much forget its existence, name and author.
And the very famous ones, I can easily tell if I won't enjoy them so I don't even try. Therefore I can't say I don't like Twilight, since I haven't even tried reading it.
Hey, wanna start a book club or something? We could decide on a book to read, that's readily available to everyone involved (for that reason I would suggest making it one available on Gutenberg or similar place), read it either in English or the original language if different than English (for those who can speak that language), and then talk about what we liked and disliked about it?