Martijn “Dino_Martino” Hellemans of the NXT STEP Mindstorms blog has been working on a motorized Lego tank that packs a lot of sophistication. For instance, he uses a MTRMX-Nx multiplexer to control both NXT servos and Technic motors. In addition to rolling around on tank treads, the tank also packs a Badass Lego Guns-style “high velocity brick cannon” aimed with a laser. He’s promising videos and build deets soon, so check back!
Motorized Lego tank with brick-shooting gun