Science fiction has a long and enduring history of imagining how our alien overlords will take over our planet (at least the dystopian visions, I rather prefer the E.T. scenario). This concept, of the great walking instrument of destruction, is as old as any, and still just as disturbing. I know it's become cliche, but take a second a think about it, can you imagine just how scary this would be? This thing lumbering down the main street of your home town, a wake of destruction behind it, certain death in front of it. There, you're welcome, sleep tight.