Panzer VIII Maus
Panzerkampfwagen VIII Maus ("Mouse") was a German World War II super-heavy tank completed in late 1944. It is the heaviest fully enclosed armoured fighting vehicle ever built. Five were ordered, but only two hulls and one turret were completed before the testing grounds were captured by advancing Soviet military forces.
Tanks in the British Army
The Cruiser tank Mk V Covenanter was first cruiser tank design to be given a name, and never deployed outside the British Isles. They first were used to re-equip the British 1st Armoured Division after the Fall of France. 
The Crusader tanks became the main British tank, the A15 Crusader Mark I and II variants had QF 2 pounder (40mm) main gun, but the 'Crusader III' was fitted with an Ordnance QF 6 pounder (57mm) main gun. It used the same main turret as the A13 Mk III Covenanter designs, and over 5,000 tanks were manufactured. The A15 Crusader Mark 111 and Mark IV finally replaced most tanks in the British forces after the fall of France and was used extensively during the North African Campaign.