Common criminals are extremely accurate with guns, while Trained FBI Agents can't shoot for shit(Face/Off)
In action movies, main characters never reload.
Cars ALWAYS explode on impact.
The good guy is always a one man wrecking crew, mowing down wave after wave of henchmen and they never, EVER have to take cover.(See Commando)
The bad guy always dies a quick, painless death, while a good guy always dies a slow, agonizing death in their friends arms.
One badass henchman always knows martial arts, and is harder to kill than the main villian.(See Rapid Fire)