Tuco's rule is from The Good, The Bad, and The Ugly. The rule is "When you have to shoot, shoot. Don't talk." Many a movie villain would have managed to wreak havoc on the world if only they'd followed Tuco's Rule.
"You see, Mr. Bond, I have already started the timer anBANG...ouch."
"Sorry, Brownfinger, it appears you forgot Tuco's Rule."