What's Your Favorite Comedy?

I thought the best way to remedy the crappy weather outside was to watch The Jerk. I like hearing people laugh, and I love it when I realize there's kids in the store right when he's talking about his special purpose. But it seems like whenever I watch this film, I'm always asked to recommend a good comedy, and I've recommended Flirting with Disaster to everyone, so I want to know what your favorite comedies are. Mine usually go unrented (I recommended Duck Soup and Horse Feathers-both of them met that fate). So tell me what you like and why, be it old or new, dry or slapstick.
Thanks,
Little Edie