This was an excellent twist, although I knew something was off when Verbal said he was in a "barbershop quartet in Skokie, Illinois." The way he said that (and not living far from there myself) made me think something was amiss about it.
Here's one that hasn't been mentioned yet: No Way Out. Get past the cheesy 80s soundtrack and it's a very taut thriller with Gene Hackman and Kevin Costner doing some excellent work. That was an ending NOBODY saw coming. I still can't believe it to this day.
"Your mother was a hamster & your father smelt of elderberries."
Monty Python

As geek as this may sound and I don't consider myself either a geek or a Star Wars geek fan, I believe the best twist ending belongs to Empire strikes back.
Putting things in perspective, nobody, absolutely nobody could have possible imagine that Vader was Luke's father. Moreover, the movie ends with Luke sort of running away from him, and we all knew at the time, a third and final installment was needed. So what was he going to do in that third and final film? Kill his father? Add to that, that we had to wait three years to find that out.
That is why I believe Empire has the best twist of all time. Psycho would come in as second.

Psycho is probably the greatest. The Sixth Sense had a great one too I am told because when I saw it I already knew the twist so I don't know how surprising it would be. Usual Suspects would be there too.
Gentleman, you can't fight in here! This is the War Room.

A Tale of Two sisters, original movie.
The Prestige, Sixth Sense and Saw could also fit well.

twists are being so overrated. It has become like "come on friends let's guess the ending of this story"
I think good twists come from writers who didn't even mean to make it a twisted-plot film. I like Saw, The Illusionist, I like the end of The Prestige but it's getting far too overrated.
The usual suspect's ending was predictable but the pin board scene wasn't. Vertigo was awesome.

Planet of the Apes ('68).

Witness of Prosecution by Billy Wilder. It was honestly more surprising that The Usual Suspects

While the movies above were good twists, the best twist ending ever for me was the end of Lost episode 4 when you find out that at the very end that
Locke was a paraplegic before the plane crash and that is why he seemed happy while everyone was suitably in anguish on the island in the previous 4 episodes. Here it is
I did not see that coming at all. Great use of camera angles when showing Locke's story before the twist.

also want to add lucky number slevin as well

I'd like to add Vertigo to this great lists!

Diabolique (1955)
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yeah this list of yours is among those whom i agree with.TUSuspects has one of the most twisted and we CAN say Most unexpected ending.The rest of the movies are also undoubtedly twisted

the usual suspects
shutter island
the prestige
silence of the lambs
fight club
12 monkeys
the sixth sense
memento

This is one of those movies where the twist completely ruined the movie for me because after then ending I have no idea what really happened. The twist invalidates the movie.

There was no twist in Alien.
Gentleman, you can't fight in here! This is the War Room.

Making guesses at the likely suspects is common. If you had heard nothing about the movie in advance, you did not guess who he was based on the intro scenes.
He did know people from the line-up, he knew Keaton. If he convinced Keaton because they wouldn't let him in otherwise, or because he knew he would need Keaton later, I don't know.
The lighter was seen in the opening scene, but it wasn't shown again until less than 5 minutes before the end.
He never spoke of himself as the devil to Kujan. He spoke of Keyser Sze as the devil and so did the other survivor.
You might have been right about a wild guess, it happens, but saying it was obvious is just plain dumb.

I suspected him since the very first scene of him interrogated by the cops. I don't have any particular reason, but then I switched to Keaton in the middle of the movie, Keaton's girl friend near the end, and finally, Kevin Spacey again. It's an easy guess at first, but then it makes me think "no, it can't be him." and I switched the suspect..that is what kind of movie this is, it's messing around with your guess. Even if you if it's the right one.
I love this movie!

So the real reason is you knew there was a twist? I wouldn't have needed your 1-6 had I been looking for a twist.

So basically you took a shot in the dark, followed it throughout, and shouldn't be that impressed with yourself? It's easy to take guesses almost 20 years after the film was made, as we had the unfortunate pre-exposure of being told it's a "twist film". It was obvious Keyser Soze had to be one of the five criminals. Seeing as Verbal and Keaton were the last two left and what followed, did it come as any surprise to you who Soze was?
I found the real twist to be that Verbal BS'd his way through everything by using the board to fool Kujan.

If you figured it out because the character's name was similar to the actor playing it, then I assume it was a lucky guess.

I had it figured ten minutes before it started

Keyzer Soze wasn't even mentioned 10 minutes in. Don't be such a hardass.

I said it was something I had to think about because in my mind I was thinking "that is the face of being surprised and then relieved", it was like one of those: HA you fooled me, good one! The only one I could think of being able to do that was Verbal, and the whole legs thing of course
Okay, I get what you're saying.
I have no doubt there were people back then who figured out the twist before it was revealed. These days, it's probably even easier to see through these kinds of twists. I do agree that the points you mentioned are hints that could be noticed, I think there are probably a few more.

oh it didn't ruin anything, just the hype I had for the fact that I thought I'd be fooled of my original thought was a bit too much. I was convinced that since I thought Verbal was Kayze he wouldn't be. Other than that not being so I loved this movie and it's most definitely one of my favorites for being really quite clever.
I said it was something I had to think about because in my mind I was thinking "that is the face of being surprised and then relieved", it was like one of those: HA you fooled me, good one! The only one I could think of being able to do that was Verbal, and the whole legs thing of course