In Halloween , during the credits at the end they list "Adult" Michael Myers as 23 years old when he was actually 21.
In the beginning of Batman and Robin when they first battle, after Mr.Freeze makes a wall of ice replacing the crashed wreckage through the brick wall after freezing Robin to trap Batman from escaping, he moves his hand on the wall like he was wiping the frost off when it was actually already clear before he taunts Batman.
Also I heard in Terminator 2, when Arnold is battling the bikers in the bar , he stabs one of them on top of the pool table, you can see the knife is plastic and bending very easily.