What makes 'cos' unique?

Note: the category and title are both clues and you may need to use some twisted logic as the answer is not straightforward

I just read the comments and Lee already had my idea! I seriously didn't catch the hints like "twisted" and "not straightforward" U and J don't count because they're straight in the upper half. I would think that they don't count. Good puzzle.

Posted by Tristan on 2003-09-22 19:50:18