title: What is the most interesting design pattern you've ever met?
body: <p>Most of us have already used the casual patterns such as <a href="https://stackoverflow.com/questions/26685/what-is-mvc-and-what-are-the-advantages-of-it">MVC</a>, <a href="https://stackoverflow.com/questions/91932?sort=votes#sort-top">strategy</a>, etc.</p>
  
  <p>But there must be some unusual solutions to unusual problems, and I'd like to hear about it.</p>