I believe that the twin-engined Dornier 335 fighter which had a propeller at both ends of the fuselage was able to jettison the rear one to enable the pilot to bale out more safely. Few entered service by the war's end. I also once read, but have never been able to confirm, that the Ju 87 Stuka could blow off its fixed undercarriage legs if a crash landing became necessary on rough ground.