WARGAMING FAKES: THE HAPPENING or WORLD OF FAKES THE GAME
These tanks never existed aside from being thought of. Such as the Jpz E-100. Even though the idea of putting a big gun on an E-100 frame was an idea formed by those goofy national socialist's, the war was so close to ending that it was a idea not worth putting any time into. Especially when the E-100 only had one frame in existence at the time as well (iirc)
Jagdpanzer E-100
The design of it is completely made up by Wargaming. The more "historically accepted" fake design something that looked closer to a Jagdpanzer 38t or Jagdpanzer IV, with a huge casemate where the gun was mounted on the front. (The only problem with this was that the gun would be way too heavy, and would put too much stress on the front suspension.)
E-50M
Pretty much completely made up by Wargaming, loosely based on the E-Series tanks the Germans wanted to make after the war in order to have them all similar in design and complexity in order to keep reliability high and part supply high as well. Although none of them, sans the E-100 were even started at all.
FV215b and FV215b (183)

It's was a cancelled projected that never really made it off the drawing board. The FV215b was planned, but nothing about it ever existed, except for the idea of mounting a 183mm gun to contest against soviet heavy tanks of the time, even then, the 120mm gun it mounts in game never existed at all.
T28 Casemate
It never existed. It's a T95 with slightly less armour for game reasons, and one less pair of tracks.
T28 """Prototype"""
It's fake.
The farthest the design got was this

and afaik even it's debatable whether it's even a real design.
Waffentrager E-100
Similar to the Jagdpanzer E-100, it was an idea that never made it onto paper, like at all.
While the Waffentrager Pz IV and Rheinmetall borsig designs were slightly historical as those designs were all about making high powered gun carriers. (although as it stood, they were more similar to SPGs that didn't carry any bullets, if I'm recalling correctly), but this one is completely made up. (Aside from the 128mm gun autoloader. That is the only thing that existed in real life.)