9. Enemy (2013)
Jake Gyllenhaal has a habit of appearing in movies with frustrating endings.
Enemy follows a teacher having an affair who discovers he has a doppelganger seemingly identical to him in every way. The audience also sees weird spider-like creatures pop up randomly throughout to give off some creepy visuals. We see giant arachnids stomping over a city, a woman with a spider head, but Jake's doppelganger and himself seem oddly chill about the whole thing.
After 90 minutes of what feels like watching somebody's weird fever dream, the ending of the film finds Adam going to check on his wife in their bedroom.
Then boom, he finds that she's turned into a giant spider that shimmies away from him in fear and then cut to credits.
It's incredibly disorientating and surprisingly scary due to it coming completely out of nowhere, with you left staring slackjawed at the screen trying to figure out not only the ending scene but the film as a whole.
There are a ton of explanations to be found online for this, including the spiders psychologically representing the women in Adam's life, biblical or political implications as well as many that simply claim it's all just a freaky dream representing Adam's worries.
That said, what most viewers came away with on the first viewing was simply confusion.