7. Orphan (2009)
In all honesty, Orphan is a horror movie with a pretty weird premise. After experiencing the traumatic stillbirth of their third child, the Coleman family adopt a nine-year-old Russian orphan named Esther. However, Esther proves to be more than the Colemans bargained for, and her sweet (but creepy) exterior hides a shocking dark secret.
The final act reveals that Esther isn’t a child at all, but a 33-year-old woman with hypopituitarism, a rare hormonal disorder which causes proportional dwarfism. On top of that, she has developed a pattern: she infiltrates a family, attempts to seduce the father, and kills the rest of the family. It’s then up to her adoptive mother to rescue her husband from the woman she believed to be her daughter in one of the strangest horror movie showdowns of all time.
The reveal is one that lives on either in horror movie infamy or legend, depending on who you ask. It’s a plot twist that’s at once shocking and ludicrous, but it’s paid off with a tense and deeply unsettling climax that makes Orphan truly unforgettable. Of course, it’s also a twist that appears to make several unfortunate and potentially harmful assertions, but it’s pulled off in a way that makes it clear that it was purely about shock value, which (sort of) makes it better.