I love puzzles, mysteries, and secret codes. Quite a while back I made up a rather complex, multi-layer code thing and put it up on the web. I posted a link to it on a couple of the more geeky mailing lists I'm on just to see who'd try it out. To my surprise, only one person cracked it - James Prescott - and he did so in a fairly short amount of time.
What shouldn't be much of a surprise though is that he's about as much of a language nut as I am.
At any rate, the puzzle's still online. If I remember, I'll put a proper link to it on the main page of the website. If you think you can crack it, go ahead and try.