DFS 194

The DFS 194 was designed by Alexander Lippisch, on his Delta series of tailless designs. Originally it was conceived to be a tailless aircraft similar to the previous DFS 40 and was going to be powered by a piston engine driving a pusher propeller. The airframe was completed for that configuration in March 1938.
The Reichluftahrtministerium (RLM - Reich's Aviation Ministry) got interested in Lippisch's designs who believed that tailless aircraft fitted much better for rocket-powered fighters.
Lippisch and his team were transferred to Messerschmitt on 2nd January 1939, to begin the work on such fighter to proceed with what was known as "Project X". The airframe was modified to host a single Walter R I-203 rocket engine (designed by Hellmuth Walter) and by October it was already undergoing engine tests at Peenemünde.
Glide tests followed in early 1940 taking the first powered flights in August with Heini Dittmar at the controls. The flight went well, and with its 550km/h (340mph) it outrun the earlier Heinkel He.176 which was tested on 20th July 1939.
It proved to have excellent speed and handling capabilities and even proved to be safe to fly at double the anticipated speed. These results gave green light for the next stage of the project, which received priority status from the RLM with the Messerschmitt Me.163 (Which used this design as forerunner) flying for the first time the next year, in 1941.

Sources: 
1. https://en.wikipedia.org/wiki/DFS_194