The MIDGARD-SCHLANGE
"Named after a demonic monster which looped the whole earth with its giant length, the hybrid armored vehicle was envisioned as both a tank and tunnel excavator to take on Allied forces during WWII - with some even hoping it could tunnel under the fortifications of the French Maginot Line."
http://www.tgdaily.com/general-scie...he-subterranean-combat-vehicle-that-never-was
http://strangevehicles.greyfalcon.us/RITTER MIDGARD.htm
................... Its pretty ingenious... basically a subterranean submarine 
................ I can't think of any weapon that could disable it.....