In Starwars: Return of the Jedi, during the assault on the second Deathstar, the
Evil Emperor lures the Rebel forces into a
trap.
The Master of the Obvious, and Admiral of the Rebel Fleet, Admiral Ackbar exclaims "IT'S A
TRAP!", after one of his subordinates says "Enemy Ships in Sector 47!"
This is fundamentally the greatest Star Wars line, and one liner ever.
Usage is widespread.