British Mk I, Panzer II, Panther, T-34, and T-55 (M1 may supplant T-55?...give it another 20 years).
Most innovative? Lots, but I hope someone mentions the T-64B....scared the bejebus out of NATO when first introduced. Bigger gun, autoloader, etc.
Most influential? MkI British, T-34/KV-1 (love reading first contact reports on the eastern front), Tiger, Panther, King Tiger...nevermind...airpower negated that one for allies......T-55, T-64, M1, Leopard II?....lots to choose from.
See this?
I've seen it IN PERSON.
I was at the Kubinka Tank Museum in Russia in 1997. Read it and gnash your teeth in envy.