Terminator's big shoot-out is in a police station with glass dividers between cubicles. I was opening fire with a machine gun full of blanks, while the effects guy was going to break the glass by shooting steel ball bearings. His device was powered with compressed air, like from a diving tank, and it looked like a full-on rifle. It had a large bore in it and fired bearings the size of your thumb. You get hit with that, it could kill you.
Just as Jim called action, I saw the stunt guys playing the detectives poised to run. And I called "Cut!" Which is something you should never do. That's the director's prerogative, and he doesn't like it when other people say the cool stuff. Jim said, "Peter, what the fuck are you doing?!" And I said, "Jim, Jim. This guy right here, he's diving through the frame right there, isn't he?" Stunt guy nodded. And I said to the effects guy, "And you're shooting there, aren't you?" Effects guy nodded. And I said, "Jim, if he dives into the shot, he's gonna get shot in the head with that steel ball bearing." Stunt guy and effects guy looked at each other. There was sort of a long beat there, and Jim goes, "Oh. Good call."