11. The Urdu Message - Iron Man
After believing he's fighting a terrorist organisation called The Ten Rings who kidnapped him in Afghanistan, Tony Stark discovers that they're actually working with Obadiah Stane, his father's business partner, who put a hit out on him in order to take over as CEO of Stark Industries.
If you speak Urdu, the plot twist is spelled out in the first act.
When Stark is kidnapped (rather than the intended assassination), the Ten Rings send out a ransom video of him in captivity. The Ten Rings seemingly spell out their demands in Urdu, which Pepper Potts eventually gets translated and realises is actually a direct address to Stane. The terrorists literally reveal that Stane is calling the shots, but only Urdu speakers would have been able to understand.