People fly backward whenever shot with a big gun.

The impact of a bullet or shotgun blast can't possibly be more than the recoil force of the rifle or gun. If the target gets thrown, the shooter will be thrown at least as hard in the other direction.

This action not only confirms that the character has been hit, it makes a spectacular special effect.

Concealed bombs and listening devices have flashing red lights.

A light, flashing or not, would defeat the purpose of a concealed device.

The lights let the audience know that the device is working.

Guns and rifles are used to make a threatening chicka sound, several times.

Rifles and shotguns can make this sound, but in movies, even revolvers can do it too. The first time the sound occurs, a new shell is moved into position, the trigger is cocked, and the weapon is ready to be fired. Every time after the first, an unfired shell would be visibly ejected.

This action provides a simple way of letting a character know that the threat of being shot is real.

Gun silencers actually work.

"Silencers" are actually "sound suppressors", which work like mufflers on cars, but not nearly as well. They turn very loud bangs into loud bangs.

There are just too many plots that are a lot easier to write if the characters can have very quiet guns, so working silencers have become standard equipment in most movies.

Bullets spark or explode whenever they hit something.

Bullets are made of soft lead or encased in copper. Neither metal sparks well when hitting hard objects. And bullets don't explode.

Sparks, explosions, and other special effects make it easy for the audience to see where the bullets are hitting.