I've got an idea for a simple robot-toy. RF controlled with two wheels, independently driven on either end of a cylindrical body. The body should be counter weighted, so that driving the motors will propel the robot forward, driving them at a differential speed will cause it to turn (steer).
I want to build this in a section of 2" diameter iron pipe. Each 'wheel' will be a pipe end cap with the threads milled out and suitable bearings so they can rotate with respect to the body.
The idea is to leave it someplace in the open and wait for the bomb squad to sent its robot out to take a look at it. At the last moment, the pipe just rolls away a few feet. A chase between the two should make for some really interesting footage on the 5 o'clock news. ;-)