Some years ago I applied for a software engineering job. To test our skills, the recruiters challenged us to write a Sudoku solver during a weekend. I have never played Sudoku before and thus had no single idea about it. But when I saw the problem, I was convinced that the right tool to use was Prolog. If my choice was right, I cannot judge. But it is a fact is that I solved the problem on time.

If you are playing Sudoku, you can use Prodoku for verifying that your solution is correct. One feature that Prodoku is missing at the moment is providing alternative solutions for the same puzzle. That's a pity, since this is a powerful built-in feature of Prolog. I guess that I'll fix it at some point.