The number one post on this blog returned by googling my own name is a post where I explain how my favorite bit of Ruby I ever wrote made my Rails controller emulate method_missing. A prominent blogger has privately described to me an amazing bit of code where he emulated method_missing in Java. I think method_missing may be the single best thing about Ruby, and you have to wonder why, when building Web apps, people don't say to themselves, "Look, we should never return a 404 error page. We should catch any 404 and implement it with some equivalent to method_missing."
Really gotta wonder about that.