Ruby Riddler is a simple quiz game, currently only with a command line interface (but who needs more :)

To install it, just type:
gem install riddler

To start a new game, type:
riddler

You can answer basic math questions, and some few text questions. Especially the content of text questions is very thin, so if you have some good quizzes, let me know, and i'll integrate them.

I'm also planning to implement a simple interface for uploading your custom questions to a central database, so stay tuned.