Air

Initial discussion around this movie decried it as a cash-grab, since it's "just" people talking in an office building. Easy to shoot, easy to light, no need to deal with weather, no stunts, no CGI, etc.

That's all true, but another way to think of it is that the script and the actors can't hide behind anything. I watch a lot of competition shows, and every time a contestant says "I'm going for something simple", the judges always say "alright, but it better be absolutely perfect". Air does just that.