Messerschmitt Me.209

The Me.209 was used to name two different projects during World War II. The first was a single-engined racing aircraft which received barely any consideration for turning it into a fighter, and the second was a fighter that would be the successor to the famous Bf.109.
The Messerschmitt Me.209 was designed in 1937 as a completely separate aircraft designed to break speed records. It was powered, like the Bf.109E, by a Daimler-Benz DB.601 engine which, unlike when it was mounted on the Bf.109, it was steam-cooled.
It was designed by Willy Messerschmitt himself who chose to put the cockpit at the back of the fuselage, just in front of its unique cross-shaped tail section. It featured also a wide landing gear, which retracted inwards mounted in the wing section.
The aircraft managed to break a speed record when its pilot, Fritz Wendel, achieved the speed of almost 756km/h (469mph) on 26th April 1939 under the German civilian registration D-INJR. The record, performed by a propeller-driven aircraft, would remain unbeaten until 1969 when a heavily modified Grumman F8F Bearcat broke it. In terms of absolute speed, it was beaten some years later when, in October 1941 Heini Dittmar, piloting a prototype of the Me.163, achieved the speed of 1.004km/h (624mph).
During the Battle of Britain it was thought about adapting the aircraft for the fighter role as the Messerschmitt Bf.109E failed to gain aerial superiority over the Supermarine Spitfire. However, the Me.209 wasn't suitable for air combat as its wings were almost completely full by the engine cooling system, avoiding the installation of any weaponry there. It also proved to be difficult to handle and extremely hard to control on ground. Anyway, Messerschmitt tried various times to improve its performance by fitting longer wings, a taller vertical-stabilizer and placing two 7.92mm MG 17 machine guns in the engine cowling. However, as the additional armament added too much weight, it ended up being slower than the Bf.109E so the project was cancelled.
Nonetheless, Messerschmitt took advantage of its designation and used it for propaganda purposes, as they hoped that the name would be associated to the performance of the Bf.109 which was already in service, albeit if the Me.209 was just a single-purpose high-speed experimental prototype.
Back in 1939 the speed record achievement was used for a propaganda disinformation campaign as the aircraft (which flew for the first time some time after July 1938) was given the name of Messerschmitt Bf.109R (which was never used by any variant of the Bf.109) to give an image of invincibility to the Bf.109 which wasn't broken until the Battle of Britain.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Me_209
2. Salamander Books - The Complete book of fighters