Most I can think of have been mentioned elsewhere in this thread, like Trainspotting, Blue Velvet, Old Boy. If you know about Requiem, you probably know about π by the same director, but I'll mention it just in case. Ooh here's a good one I should have put in the main thread, too late now lol: Die Welle (The Wave). It's a German drama that takes place in a high school, that's all I'll say about it, but it's really good.