The art of the twist is one of the single most rewarding things in scriptwriting. If done satisfyingly, it's the kind of pay-off that justifies complex build and intricate seeding (assuming you're not just one of those lazy writers who pulls something out of your ass to make things interesting in the final act) and it ends up being its own reward.
That's why so many film-makers still seek to pull a fast one on their audiences. There's a currency to twists that you just don't get with straight endings and the potential for word of mouth promotion increases exponentially when prospective audiences get wind of a Big Twist (as long as it's not spoiled).
There's another layer to the twist though, which can be even more satisfying. That comes when a confident film-maker teases the audience with some trickery that actually reveals the magic of their twist early on in the movie. They effectively show a flash of the bunny inside the top hat before the grand reveal, and in hindsight, it just makes the "con" of the twist even more clever...
12. The One Man Fight - Fight Club
In one of the most famous twists in the entirety of Hollywood history, the end of Fight Club reveals that Tyler Durden and the Narrator are in fact one and the same. Durden is merely a projection of everything the Narrator wanted for himself: swagger, confidence, activism, anarchy... And the only way he can stop him is to kill that part of him.
There are vague hints that Durden isn't real all the way through, which you can pick up on subsequent watches - like the single frames of Brad Pitt spliced in - but they're nowhere near as revelatory as the scene that sees the Narrator beat the sh*t out of himself.
As he seeks to blackmail his boss, he assaults himself viciously and wrecks the office, not only giving a hint that he's unstable (to say the least) but also cheekily foreshadowing the twist reveal by saying “For some reason I thought of my first fight … with Tyler.” He might as well have just help up a sign saying "I was fighting myself alone then, too."