Before I begin, note that every word following this is considered a major spoiler for the film.
So, what would happen if you threw Men In Black, Cube, Hellraiser, and most every scary-secluded-cabin-for-teenagers movie in a blender? The Cabin In The Woods would happen.
This is the film from 2012 from Avengers wonder-boy Joss Whedon and Drew Goddard. I loved this movie. It turns the genre (if you can pick just one) on its head. I loved that — despite it not taking itself too seriously, despite it having a good sense of humor — it painted a deep mythology. I loved that it dared to explain not only why we love monster, ghost, and zombie movies, but also where these creatures all come from and what their purpose is.