Here's a good start to a Lego Pinball Machine.
Despite the fact that I really don't like pinball machines, I have thought a lot about building one. But the one I dream about would be epic. It would be absolutely huge and the ball would probably be the ball that came with the NXT 1.0. I dream of making it fit onto a 4x8 piece of plywood. It would be three dimensional and multilayered. Lots of motors and tricks much like the Great Ball Contraption.
I envision having maybe five or more balls in play at any one time. It would be a machine that would take all of your concentration and peripheral vision to play. You would feel the urge to just watch the balls race around, but while you are watching one thing, another would require your attention. There would be several paddles and controls all over the playing field, but not all of them would be the type of paddles typically found on pinball machines. There would be gates, levers, seesaw devices, and all kinds of stuff that could be controlled, but points would only be scored if the device was triggered at the right time.
I would put challenges in the game, such as if you hit a target five times, an extra ball would would be entered into the game, but if other targets are hit a gate would open for balls to roll off the playing field. I would put several challenges all over the game so that you wouldn't have to focus on just one challenge.
You may have to bend to one side to see the ball and time your actions for one challenge, while another you may have to stand on your tiptoes to see the ball. Think about how the Wii changed video games, the pinball game I envision would be just as interactive.
The game would have a very high degree of kinetic art involved. You wouldn't only see balls rolling around, but tons of moving things that would distract the player's attention.
Here are some great inspirational videos
Like I said. Epic