For a straight turbojet, the P&W J-52 was first run in 1955 or so. It was developed for the Hound Dog missile and the A-6 Intruder, was put in later versions of the A-4 Skyhawk (E through M, plus several export variants), and is still in active service in the EA-6B Prowler. The civilian version was the JT8D that powered some 727s and DC-9s. I don't know how many JT8Ds are still in service...