The Birds. The Exorcist. E.T. The Wizard of Oz. The Texas Chain Saw Massacre. If the mere mention of one of these movies didn't freak you out as a kid, you must not have seen them.
For me, it was Jurassic Park. Seriously, reptiles the size of buildings with teeth the size of children, and a hankering for human flesh? Velociraptor attacks were the subject of nightmares for months.