Although I'm quite familiar with Mathematica, I always try to keep an open mind and don't use it as golden hammer. Officially, I'm working in image and data processing, but in my free-time, I'm particularly good at things that are fun, for instance

• glueing QR codes on paper roles and writing articles about it
• implementing a Mathematica plugin for the best IDE ever just because I was curious whether I can hack a complete Mathematica parser
• making images that give you a headache
• making stackexchange better by hacking a highlighter for Mathematica code-blocks in Java Script or abusing others hard work to extend our own markup editor on mathematica.se
• I love making music. Especially with my friends.