puppet, your mine cart idea has made me think of so much that would be awesome.
Picture this:
You are walking through a mine (futuristic mine) and there is one of those cable cars in it (the ones that hang from the ceiling) there is a plasma barrier blocking the way into the mine, that hurts you when you touch it AND you can't move through it.
So you have to find a switch which activates the cable car which goes OVER the barrier and into the mine.
Then it could be like an on rails shooter for a bit..... the cable car going through the mine, you shooting aliens down left right and center.
Then the cart stops, you move on..... and you get the picture.
E.D.
P.S. For those who don't want to read that, I was basically complementing puppet on that idea he had, as it just opened up millions of possiblities *adds "model train" to list of current projects*