If you're man enough, watch all of Darren Aronofsky's = Pi, Requiem for a Dream , The Fountain.
Ong Bak - one of the best contemporary action movies.
CLOCKWORK ORANGE by Stanley Kubrick
Spoiler: I've watched (click to see content)
Seven, The sixth sense, Fight Club, Sin City, Pan's Labyrinth, Requiem for a Dream, American History X, V for Vendetta, Unbreakable, Trainspotting, Saving Pvt. Ryan, Snatch, As good as it gets, Donnie Darko, Saw.