What could you code in four hours?

If you were allotted four hours to program anything you wanted in any language and environment, how much could you accomplish? What tips would you give to be productive?

Let's say these four hours include planning time, and any test cases/docs that need to be created. I'm talking production work.

I've heard about people coding thousands of lines of code in a few hours, how would _you_ accomplish this feat? Creative ideas and mind hacks welcomed :)