Automatic dead code removal for jQuery?

I'd like to hack out a whole ton of unused jQuery JS from my website.

While it's possible to get a custom build, I'm more or less just guessing at what to include, and haven't actually gotten it right yet, and end up with missing/broken features.

Does anybody know of an app/website/browser plugin/etc. that will produce a .js file that contains only the code that's actually used?

This seems like a perfect job for the browser, since it knows what's being called and Chrome already has a coverage tool, however I don't see any way to export the necessary code or delete the dead code.