The Awful Truth, 1937, starring Cary Grant and Irene Dunne

There's a moment where the estranged Grant and Dunne are the only ones in on a joke, a joke designed by Dunne to enrage Grant and ruin his most recent engagement. And it does enrage him, a bit, but it also delights him--and somehow, even in the grainy black and white, you can see his eyes smile before his face does. 

It's one of the most romantic scenes I've ever seen and the film is one of the best Rom-Coms of all time. To feel like you've only been briefly allowed to witness the private music between two people--that's the good shit. I can trace the start of all of my romantic relationships to that type of moment, where the eyes meet and the electric note sounds. And what's more, the writing and delivery are so sharp and funny. I've seen it at least ten times, including (fittingly) the night of my second wedding, and each time I laugh. It's good shit, though it might make you wish this type of on-screen chemistry and charm weren't currently in such short supply.