Plot hole: When the deputy arrives at the sheriff's house, Michael gets out and leaves the door open. The deputy comes out to the car and sees it open. And he thinks nothing of it, despite knowing he didn't open it. Logic would say, "Well someone else opened it."
Plot hole: Near the end of the movie, Jamie and Rachel are being taken down the highway to safety by the vigilantes when Michael climbs into the back of the truck from being underneath it. Michael then struggles, stabs, and violently throws two of the vigilantes from the truck, and the third vigilante, standing only inches from the other two and still holding guard in the back of the truck, appears to see or hear none of the commotion. Impossible, even for horror films.
Plot hole: At the end of Halloween 2 Michael is completely engulfed in fire for several minutes. Even if somehow he was to survive he would be covered in scars. When we see him at the beginning of part 4 he has a few small scars on his arms. Same with Loomis, he has a few small scars on his arms and one on his cheek despite being in a gigantic explosion and fire. Obviously this was done so they could bring the 2 characters back but it still makes no logical sense.
Plot hole: Toward the end, when Jamie and Rachel are being taken to safety by the vigilantes, Michael suddenly climbs over the back of the truck and slays all the guys one by one. There is no way he could have been 'hiding' under the truck as he was still deep inside the school when the truck sped out of the lot and down the road. Obviously added for dramatic effect at the end.