I'm probably waaaay late, but here's what I'm doing for the original Rock Cannon. I'm basing it off this tutorial: http://www.youtube.com/watch?v=lZWXU...ure=plpp_video
I'm using a cardboard tube from Home Depot as the main barrel, and then I'm actually using a Quakers oatmeal tub as the smaller tube. In the tutorial, he has a bunch of funky shapes on it, but you can just cut all those off and such.
I'm not sure about the lights, but it looks like someone else has already covered that.