I know this isn't always considered one of their best, but it's my personal favourite if only because it was the one I watched repeatedly/obsessively on VHS as a kid. i love the fact that Rogers only really begins to fall for Astaire once she realises he's actually a tap dancer more than a ballet dancer. It is through the dancing that their most profound feelings for one another are expressed. Great screwball script.
Delightful. There's a having-your-cake-and-eating-it-too class consciousness that only old Hollywood could pull off, a faint sketch of a romance and some light-as-air bedroom farce. There's Edward Everett Horton as the adorable boob (never better). And, of course, there's the raw beauty of motion to make you realize the transportive and emotive power of celluloid that transcends any one film.