Which tanks were most beneficial to the Third Reich?

I know that everyone has heard of the Legendary german Panzers. And as well as the monster TIGER Tanks that the Nazis mass produced during world war 2. But I am not looking for the big names. I am looking for some Tanks that were the most helpful to the German Army. You know, tanks the untrained mind might not have heard of; Panther for example.

Now, I know there was more than one type of panzer and tiger. So please tell me. Which of the German Tanks was most beneficial to the Third Reich

Oh, and which tank was it that had an open turret (where an foot soldier could just walk up behind and take out the entire crew)

Your probably thinking of Mobile Artillery. Something like this http://www.achtungpanzer.com/wespe.htm

However I think the Germans did their best with the Panzer III or IV. Captured the most ground with these versions.

Not a tank, The Stug III series.

Yes. The Panzer III & IV were, while not as ‘sexy’ as the Panther or Tiger, highly versatile machines that were the backbone of most German armored formations. Continually modified throughout the War, a Panzer MkIV was capable of holding its own against a T-34 and outclassed the first generation M-4 Sherman completely…