Battle Royale
You probably didn't know this, but it's widely assumed that this movie inspired The Hunger Games. Much like how The Hunger Games introduces its premise, Battle Royale selects several young individuals from a Japanese grade school and isolates them on a remote island. The students are then forced to murder one another until only one remains.
Banned, Not Bad
Battle Royale kept its drama and dark humor at the forefront of their movie the entire time. Fortunately, because of the time period (the movie came out in 2000), this movie became a cult classic and it did not disappear into unspoken history. This movie was banned in several countries (it's still banned in Germany), but it's considered to be one of the most successful Japanese films ever.