Making Memorable Lessons and Activities

MissCalculate's blog post about making a memorable project got me thinking about how important that is for teacher's to accomplish.  Students are probably given thousands of assignments throughout the course of their education; I think you've done well if you manage to leave one or two of those things permanently etched in their memory as a cool, fun, exciting or unique activity.

What are some of the lessons, projects and activities you still remember fondly?  Some of mine:

• I remember we did a whole unit on mysteries centered around The Westing Game (which I mentioned here).  It was fun and led up to role-playing and writing our own mysteries!
• In middle school, we had a great unit on literary archetypes that was based around the original Star Wars trilogy.  For weeks, we watched the three films and connected archetypes to Luke Skywalker's adventures, and we were all well-equipped for lit analysis in HS thanks to doing so.  
• One year, we explored the concept of parody by making and recording our own spin-offs of popular TV shows, to hilarious results!
• In chemistry class, we once made ice cream!  I also recall being impressed by one lab where we constructed a filtration system with plastic water bottles, which turned muddy, brown water into clear, "clean" water.

What about you?