Time travel/ deja vu:
- Triangle
- Probably not what you're looking for, but Irreversible is told in reverse order.
Body Snatching/duplicating:
Scooby Doo:
- Bay of Blood (60s), and I'm sure lots of other giallo
Elimination:
- Battle Royale
- Cabin in the woods
Dream horror:
- Insidious had kind of a dream state thing, which I thought was kinda cheesy
- The Fourth Kind has some good hypnosis scenes