Repo Men has a brilliant twist at the end. I won't spoil it for anyone who hasn't seen it but it took me by surprise!
I would say it depends largerly on how the MC develops, how well he or she develops (meaning the quality of the portrayal of the process of MC's development). A pretty good twist, I think, comes with a pretty well developed character. How the game is set, what are the attributes and how they come into play. I also think that the uniqueness of the plot should not be at the quality's expense.
I don't know about the greatest twist, but it would be a big twist to write plot in which the protagonist turns out to be the antagonist. No doubt it's been done many times, but I can't recall an example at the moment. Maybe something like this: A serial killer is striking at random in a particular town. Totally senseless killings with no discernible pattern among the victims. Some are male, some female, some old, some young. There are only two uniformities: The killer always uses the same .22 caliber pistol (the police have identified the bullets -- same gun every time), and he always leaves a token at the scene, a black chess knight, as his signature. One day after three killings have occurred and the town is on edge, Joe Protagonists (a respected and respectable man about town) finds a chess knight outside on the sill of his kitchen window. This is unnerving to say the least. Is someone playing a sick prank on him? Or is the killer marking him as the next victim? A day or two later a bullet pierces the windshield of Joe's car and lodges in the padded headrest, an inch from his head. He drives directly to the police station. They dig out the slug, send it to the forensics lab. Sure enough, it matches the killer's gun. Joe P is terrified. He begs the police to give him some protection. They assign a man to watch out for him, but they can't be with him 24/7. They help him install burglar alarms in his home. They send him to a firearms course and issue a permit to carry a concealed weapon. Meanwhile a woman in town, Molly G, finds a chess knight in her mailbox. She, too, is terrified. She's a widow with no family to help protect her. Like Joe, she contacts the police. They introduce her to Joe, who encourages her to take the firearms course as he did and start carrying a weapon. But alas, Molly is killed. One .22 bullet in her head. It's from the same gun as the other murders. Use your imagination to string this story out. Perhaps Joe receives another cryptic warning that he may be the next victim. And in the end, it turns out that Joe is the serial killer.
I, personally, am not a fan of the "it was all in your head" ending. I find it cheap. "Well guys, I know you've been wondering what on earth is going on and here we go, build up to the climax and BAM...CRAZY. The end." Reminds me of Lost. To add to what others have said. The best plot twist is one that takes the reader completely by surprise, but once they know, they set their book down and say "Of course. How on earth did I miss it?"
"And then he woke up...and realized it was all a dream..." Never, ever, use that conclusion. In all seriousness, I find the best plot twists to be depressing ones in that perhaps a major character dies or disappears at the last minute. Simple, I know, but I seldom come across it nowadays.
I love it when the plot twist is something I didn't see coming but could understand after it happened. However I absolutely hate it when a plot twist has that forced feel and it takes the twist a step too far so that it doesn't really make sense. The death of a major character other than to tie up loose ends is always a good one. I find that the all in your head twist can work if it isn't shoved down people's throats I read a book where it didn't explicitly mention that it may not have been real but many people reached that conclusion anyway and it really resonated with me because of it.
Doctor Who twists... the famous one... your wife shoots you while your wife watches.... with your best friend watching who is pregnant with your wife.... Didnt see that one coming.... LOL
Well, if you're going THERE, how about Captain Jack talking to the Doctor about his home in the Boeshane Province. And as the first person from there to enlist in the Time Agency, his neighbors nicknamed him the Face of Boe...
If you want to go with some cliche ones like "Mentor is the true villain" or "Evil guy is only evil to stop greater evil" then you need clever foreshadowing that people will only really understand the second time they read.
My personal favourite plot twist was the end of the movie "The Usual Suspects". That was (and still is) amazing.
The greatest plot twist in my eyes is when a story SEEMS to be about one character, but then a side character is actually the main focus of the story.
Have you ever seen Inception? It must be the most clever movie ever made. Not only is the entire movie about "Inception", which is planting an idea in someones mind, creating something that's impossible to let go. BUT, by the time the movie is over, that is exactly what the director has done to the audience. The film plants an idea in the mind of the audience that's impossible to let go. The ending (which I wont spoil) is sort of a plot twist, but its the idea that keeps you thinking long after the movie is over. Much more effective than the "OH" moments of some other plot twists.
Spoiler: 1984 Spoilers Yes, like in 1984. There is no good reason to believe that Winston and his girlfriend can overthrow Big Brother. There is no reason to expect a fairytale ending, yet that is what the reader desperately wants and expects to happen. Because of this, the scene in which the love nest is intruded upon, in which the charade is abruptly shattered, is emotionally distressing. Winston had just finished his inner monologue about how hopeful he was, and the reader shared that hope, only to have it duly snatched away. The emotional roller-coaster doesn't end there, the reader continues to hope for and expect that Winston will somehow get out of his mess. The finale, where Winston's fall is completed, comes as yet another surprise that everyone should have seen coming. Those unexpected 'plot twists,' which were totally predictable, are what make 1984 so incredibly powerful, not the social commentary. Spoiler: Lolita Spoilers Lolita is another story where I was totally surprised by an obvious ending. When I first watched the opening scene (yes, I watched Kubrick's film instead of the novel, shame on me), I was convinced that Quilty was the bad guy. I was convinced that he was some sort of devious abuser, and that Humbert was rendering justice when he killed him at the start. But as it went, Humbert was revealed to be the abuser, while Quilty was the saviour. I rewatched the opening scene a second time, and those key details, like Humbert being drunk, which I had overlooked before, stood out. In retrospect it was totally predictable that Humbert was in the wrong, but my expectations blinded me to the obvious details.
