What is (or was) your favorite assignment (or unit or lesson)?

A recent article on focusing on what we're doing right made me think of one of my favorite lessons- an interior monologue workshop I did in my introduction to acting class that found my students and I watching part of an episode of the The X Files, recording our guesses about the internal monologue of one of the characters, and then debating the evidence as to why our particular interpretations were the most accurate. It was a fun way to dig into a piece of particularly heady curriculum and even though I haven't taught those students in a long time, they still bring it up when we see each other.

So now I'm curious- When you think about what you're teaching this year (or what you've taught in the past), what lessons or assignments come to mind for you as particularly memorable?