The Day After (1983)

Revealing mistake: When Denis runs out into the field after the nuclear attack, she brushes up against a dead cow, and the cow moves like a stuffed prop. Real cows are much heavier than that.

First Air Force Officer: Confidence is high. I repeat, confidence is high. Roger, we've got 32 targets in track and 10 impacting points. I want it confirmed... is this an exercise? Roger, copy. This is not an exercise.
Second Air Force Officer: Roger, understand. Major Reinhardt, we have a massive attack against the U.S. at this time. ICBMs... numerous ICBMs... Roger, understand. Over 300 missiles inbound now.

Trivia: The US department of defence did not allow the producers to use stock footage of actual mushroom clouds so they had to rely on special effects of the time, which is why the clouds appear so fake. They also wanted the script changed to state that the Russians started the war.

Mercury