Major spoilers ahead!
1. Frailty (2001)
Frailty kicks off with Fenton Meiks confessing that his family used to kill people as "God's Hands". See, his dad claimed an angel told him to axe-murder folks who were actually "demons". Fenton never believed it and even turned in his own brother, Adam, who continued the spree. Now here's the kicker: The man who uncovers Fenton's story turns out to be Adam, who kills the FBI agent and walks away free. This is one unholy twist.
2. The Others (2001)
Nicole Kidman plays Grace, a woman living in post-WWII Jersey with her two photosensitive kids. Their mansion is dark and creepy, and soon enough, ghostly things start happening. Doors open on their own; curtains are mysteriously drawn back. Eventually, we find out that Grace and her kids are the actual ghosts, and the "hauntings" were the new living occupants trying to rid them.
3. Timecrimes (2007)
Hector is your average dude who just happens to spy a lady stripping in the woods. Being a creep, he investigates and gets stabbed by a guy with pink bandages. He escapes to a lab where a scientist convinces him to hide in a time machine. When he comes out, it's an hour earlier, and Hector 2 tries to fix the timeline. But get this, in his efforts, he becomes the bandaged stabber, and the cycle repeats. Confused? Good, that's the point.
4. Triangle (2009)
Jess, a troubled single mom, goes on a yacht trip that turns into a nightmare. A storm hits, and they take refuge in an abandoned ocean liner—except it's not so abandoned. They get killed off one by one by a masked murderer. Jess realizes she's stuck in a time loop and tries to break it by becoming the murderer. Each loop has her making more drastic decisions, but she never quite escapes.
5. Exam (2009)
Eight candidates are in a room for a job interview from hell. They're given a blank sheet of paper and told they have 80 minutes to answer the question. What question, you ask? Well, that's the twist. Turns out, the answer was to do absolutely nothing. The whole test was designed to find the candidate who can follow the employer's ambiguous instructions to a tee.
6. Identity (2003)
Ten strangers find themselves stranded in a Nevada motel during a rainstorm. They start dying off, one by one, in the order of their room numbers. Ed, a former cop, tries to solve the murders. The bombshell? They're all figments of a killer's dissociative identity disorder, played out in his mind. As each "identity" dies, it disappears from his psyche.
7. The Machinist (2004)
Christian Bale lost 60 pounds for this role, and trust me, it adds to the horror. Trevor is an insomniac machinist who starts seeing weird stuff like coworkers who don't exist and mysterious post-it notes. His life spirals out of control. The kicker? The "coworker" he thought was plotting against him is actually his own guilty conscience for a hit-and-run he committed.
8. Hard Candy (2005)
Elliot Page plays Hayley, a 14-year-old who lures Jeff, a suspected pedophile, into a trap. She drugs him and ties him up, all while subjecting him to psychological torture. Hayley seems to be getting her revenge for a missing girl named Donna, but the twist is jaw-dropping. Hayley didn't know Donna; she's simply a vigilante out to punish predators. She traps Jeff into hanging himself and walks away to find her next target.
9. Moon (2009)
Sam is an astronaut nearing the end of his three-year stint mining helium-3 on the Moon. He starts seeing things, has an accident, and wakes up in the infirmary. But then he finds another him, still injured from the crash. The twist? They're both clones with a three-year lifespan, designed to think they're the original Sam who will return to Earth. When one clone's time runs out, another is activated.
10. Buried (2010)
Ryan Reynolds gives a claustrophobia-inducing performance as Paul, an American contractor in Iraq who wakes up buried alive in a wooden coffin. Using a cellphone, he negotiates with his captors and tries to get rescued. In a heart-wrenching twist, the rescuers dig up the wrong coffin, belonging to another captured soldier. Paul is left in the dark, literally and figuratively, as his air runs out.