Some time ago, I got asked to submit an answer to one of the scripting games challenges. I agreed, thinking I'd get a meaty admin puzzle to work on. Instead, I got a more classic computing problem - calculating prime numbers. Turns out there's a very ancient algorithm, the Sieve of Eratosthenes that can be used. So after a few minutes scratching my head (to work out how the algorithm atually worked), I managed to get a solution which you can read at: 2008 Winter Scripting Games: Advanced Windows PowerShell Event 6 Solution.
This challenge was not an administrative problem, so the solultion may not be all that interesting to IT admins. What was interesting was the fact that you could PowerShell to do this sort of programming - it's a great proof point to the quality of the PowerShell scripting language.