13. The Ginormous German Tank
The Panzer VIII Maus was the heaviest tank ever built. It measured about 33 feet long, 12 feet wide, 12 feet high, and weighed almost 200 tons. Its secondary armament was a 75mm coaxial gun instead of a machine gun.
Its main gun was a 128mm monster capable of destroying any Allied tank at ranges of up to 2.2 miles. Even that was not enough for Hitler, who thought that the 128mm looked like a toy gun on the Maus. So he ordered the gun increased to 150mm.