I have another favorite shot. This one, too, is from "Balance of Terror."
Spock reports that among the debris from the Romulan ship is a metal-encased object. Kirk correctly determines it to be a warhead and quickly orders phasers to blow it up--but it's really, really close to the ship. It blows up, the ship shakes, the camera tilts and everyone falls out of their chairs. But in this case, all the power and lights go out on the bridge. No overhead work lights, no monitors, no colored blinky lights on the consoles. Nothing. The bridge is in complete darkness for a shot that last five seconds--complete darkness except for two lights on the bridge: