Suggest any, but please do not state the twist in the comments :)
It has to be a reveal, something that changes what you've been watching rather than simply revealing a surprising new element. With twists like these, you can watch the film again with new perspective. Twists like the killer in a murder mystery being a main character or something, whereas in the opposite kind of twist would be the killer having been someone spoken of but not well known. Twists like the end of Se7en, though truly shocking and rather unexpected, do not count. However, the reveal of the killer in the film, is closer to counting (though it still does not quite count). Hopefully this gives you a good idea of the twists we're looking for.