[dgunn]

If you're going to build something specifically for this interviewer, you should make it useful to him/her or to his/her company.

Maybe think of some data their company would find useful and give them a good way to consume it / interact with it / take action on it.

Without explaining any details, this may be the best answer you'll get. People won't spend much time commenting when all they can really recommend is another generic list application or something.