Poltergeist (1982)
When creepy and unnatural things start happening to an average Californian family this family turn to an exorcist for help. Initially, the spirits start friendly and playful but then something terrible happens and they become unexpectedly evil.
Gremlins (1984)
A gadget salesman is looking for a special gift for his son when finds something at a store in Chinatown. When a young boy is given three specific rules for his new pet he accidentally unleashes a clan of malevolent monsters that create chaos in a town.