The Russian T-34 is generally agreed the best all-around tank in the war. The Germans were surprised, first by its capabilities and then by the staggering quantities produced by Soviet industry. The T-34 was a simple and rugged design. Its reliability was legendary. There have been T-34s pulled out of bogs in recent years that, after some clean-up, worked perfectly. One example found in an Estonian bog is here. WW2 tanks were notoriously finicky, especially German tanks. Not the T-34. It was built, well, like a tank. The platform was exceptionally flexible. Armor, gun and engine were all improved through the war. The picture above is a 1943 model with a big 85mm gun.