I dunno fellas, I guess we have to take into consideration what we consider to be an uber-weapon. This is open to discussion in itself.
Obviously, the ultimate uber-weapon of 1945 is the A-bomb...working downwards from there...
The overwhelming majority of the drawings that appear in the Luftwaffe '46 books are science fiction, but, were still within the reach of the designers had they additional time and resources to create them. Some of those became actual aircraft, whether or not they flew or reached operational status (a heated debate in another thread!), we can't deny that engines were being bolted to radical airframes.
Much of the technology taken from the Germans in 1945 was implemented into both US and Russian aircraft production, if more for testing than anything else. When one compares the Triebflügeljäger to the XFY Pogo, the Ta-183 Huckbien to the Bell X-5, or the XF-92A to some of the proposed Lippisch designs, its obvious that much of this wasn't fantasy.
I do have several books on Luftwaffe Secret Projects, though, and some of this stuff is out in left field, such as kerosene-propelled pulse jet intercontinental bombers, etc. For the most part, though, I don't think these guys were dreaming up stuff that required a flux capacitor.