Choke, by Chuck Palahniuk. The, uh, ending of this book is vile. Hilarious, but vile. I have two words for you. Anal. Beads. Yes, the “doctor” being revealed is one hell of a plot twist, but the final scene of the book floored me. I’d forgotten all about the beads. Just goes to show you, what goes up, must come down.
And, yes, there are better plot twists and endings out there, but this one stands out in my mind the most.