The swept wing fighter. Although the Me-262 had swept wings, it wasn't originally designed to be that way. The original concept showed conventional wings. Note also that the fuselage was also rather conventional, being oval in this drawing rather than the triangular cross section that we're familar with.
The reason for the triangular fuselage was to accommodate a more conventional main landing gear layout. Folding inward without rotating the wheel assembly (as shown above) would have meant a large bump on top of the wing, and the wing was too thin for the wheel and strut. Simply widening the bottom of the fuselage covered that problem.
As for the wings being swept back, balance problems came about when the anticipated BMW 003 engines proved to be heavier than originally planned for, and so the wings were swept back 18.5 degrees to allow the engine pods to move rearward. The inside wing root was still unswept at this time as shown here:
The original flying prototype also included a front piston engine and propeller, which proved fortunate when both BMW engines failed on the first flight. The first six flying test aircraft were tail draggers, as the tricycle landing gear used on production models was still being developed.
This version showed wing stall problems at the straight section, and wind tunnel tests showed that it would fly better if the whole wing was swept. So fairings were added to the wing root section starting with prototype #7, ending with the final production wing looking like this:
Due to further promising results with wind tunnel testing, further swept angles were tested; The VII version with both conventional and V tail designs had a 30 degree sweep, while VIII went further with a 45 degree wing.
The VIII also had the engines moved to the wing roots, and was going to use the newer and more powerful Heinkel HeS 011 engines. Neither of the later two designs had flown, they were in the wind tunnel test stage when the war ended.