Night of the Living Dead (1968)

Factual error: In the 30th Anniversary version with new footage it is revealed that the first zombie we see (the one that kills Johnny) died in the electric chair. If that's the case, he should be bald with a large burn on his scalp, but he has a full head of hair.

Factual error: The truck's gas tank is said to be empty, but is able to explode spectacularly later on. An empty gas tank may spout a jet of flame, but will not have enough force to rupture and damage the truck, a full tank of liquid gas will not burn unless vaporized. Simply put the truck would not explode in that Michael Bay fashion.