Lord of the Rings: The Return of the King - Seeing the Future ... but It's Not There
In LOTR: Return of the King, Aragorn wrestles with Sauron by looking into the Palantir. Sauron reveals a vision of Arwen dying, causing Aragorn to stagger and drop the stone; when he does, the Evenstar he is wearing (gift from Arwen in LOTR I) shatters into pieces.
BUT -- in LOTR: The Two Towers, when Arwen is leaving Middle-Earth, she has a vision of Aragorn and her son-to-be, who is wearing the Evenstar! The camera even zooms in on the jewel so we can't possibly miss it. Arwen is clearly meant to believe this vision is true, as are we; but if the vision IS true, the Evenstar can't shatter into pieces later on. Somewhat of an existential conundrum, true; but the scriptwriters should have caught this (neither scene is in the book version).