The first operational rocket-powered aircraft in the world and the only one of its type in World War II, the Me-163 Komet was an extraordinary leap in aviation technology. Even though it's performance was unrivalled by any aircraft at that time, it was an extremely dangerous aircraft that was not suitable for the role it was designed for, a fighter, or any others. In fact, more Luftwaffe pilots died in accidents in either landing or take-off than in combat. The problem is the Komet's highly explosive fuel that surrounded the cockpit which made it very, very hazardous to even be inside when the engine is on. In the end, the Me-163 was given up in favour of the Me-262 Schwalbe, which was much more successful and deadly.
A pilot boarding a Messerschmitt Me-163 Komet. The first operational rocket-powered aircraft.