This was a cool scene from ” Aliens: The Director’s Cut”.  The Colonial Marines stranded on the Alien planet set up robot sentries in the hallways of the complex where they are trying to survive.  The sentries detect motion and are programmed to fire upon any intruders tripping the sensors.  Needless to say, the ammunition runs out fast as the Marines figure out that they are overrun with deadly Aliens trying every means possible to get to the Marines.  Very effective editing and use of sound effects.  We don’t ever clearly see the Aliens being blasted into smithereens by the hyper firing robot machine guns.  Nice sequence.