Not so long ago, I posted a programming challenge, and received solutions in many different languages. Just when I thought people had forgot about this, I got this one from Anton Triest. It was written in a programming language called ... (surprise) XSLT!
Ask not what you can do in XSLT; ask what you cannot do in XSLT. 🙂
(For those of you concerned that you need to buy an XSLT compiler to try it out, take heart -- all you need is your web browser)