People hit by bullets or shotgun blasts flying backgrounds, often through windows. (Newton's laws tell us that, if this were the case, the person firing the gun would also be flying backwards).
Bad guy extras only need to be shot once, anywhere in (or even near) the body, to go down. The good guy can be shot a dozen times and appear only to be suffering mild muscle aches.
Twelve guys with 50mm cal. machine guns can't hit the hero who is ten feet away in an empty closet with the door open. The hero can shoot the balls off a gnat in a hurricane with a pistol at 100 yards.
Time-bombs always have convenient read-outs telling you how much time is left.
... and the timer always beeps with each second.
Explosions always happen in slow motion. When an explosion occurs, make certain you are running away from the point of detonation so the blast can send you flying, in slow motion, toward the camera.
Sound Clichés
Every button you press on a computer makes some kind of beep.
Text being spelled out on screen (whether computer or lower third) MUST make some sort of typing and/or dot-matrix-printer type of sound.
Helicopters always fly from surround to front-speakers.
People standing outside a running helicopter can always talk in normal or just slightly louder than normal voices.
Characters will never hear an approaching airplane or helicopter, even though in real life you would hear them approaching for at least a minute before they were close enough to see. This also holds true for approaching armies on horseback and tank battalions.
Kids can always whisper even if their two inchs away from a villian - he won't hear. If they step on a branch however, the villians will immediatly know its not some animal, and catch them.
Motorcycles usually change from Harley Davidson choppers when engaged in highway operations to Yamaha Dirt bikes when operated off-road (as in "Then Came Bronson").
It is now the modern era, and thus, sound has been installed in space by the elimination of that nasty vacuum problem.
Explosions in space make noise.
Guns (handguns, rifles, machineguns etc) have a really deep "BOOOMMM!!" sound not a "CRACK!". Also, the there's old cliche about the number of rounds the average magazine holds, the good guys almost never run out of ammo, and they seem to be able to use a handgun accurately to over a 100 meter range (accuracy of weapons over distance is pretty much a factor of barrel length - handguns are for CLOSE distances).
All sub machine guns sound alike and have the same rate of fire.
Machine guns and their rate of fire ... most users of these weapons can manage to sustain over 10 second continuous rate of fire (in actuality, you are supposed to fire the things in short bursts -- after a long burst the barrel will heat up so much the weapon will jam). Also I have never ever seen any protagonist change a MGs *barrel* no matter how long he has used the MG. (the barrels overheat, and also sustain incrediable wear requiring these to be changed -- often in battle, the gunner's mate will carry spare barrels as well as the inexhaustible ammo supply which weighs next-to-nothing). Esp. WW2 era weapons.
Bullets always ricochet, and they must travel pretty slow because the "rico" is 1/2 second later after it moves 50 feet
All bullets make a distinkt riccoche sound and when flying past you they make a zip noise when in fact they are moving faster than the speed of sound and in real life would produce a whip lash or bang sound.
Handguns: All handguns make a frightening clicking sound when handled as though to suggest that the parts are loose. The more advanced the gun (Men in Black) the louder, and more varried, the clicking. In real life any gun making noises like that would probably explode in your hand with the first discharge. Note: All energy type weapons will power up with a loud hum.