Hovercraft...
or better yet, get ahead of the curve from Back to the Future, a hoverboard. lol.
What would be cool is a tank that shoots t-shirts. I mean like turret and tank treads and a cool shell to make it look like a tank. As well, you can put lights and stuff on it and also rig up a stereo and have it blast ACDC as it fires a t-shirt. That would be awesome.
Maybe go for a robot that does a laser light show. That would be cool, though it wouldnt have to move much.
