Easy: Victory Games’ James Bond: 007. I bought a first edition copy in 1983 and have used it until about 2010, since when we haven’t had an espionage game running. Partly, this is a function of having worked in the industry, partly it was a response to the real life asshattery of the Global War on Terror.

Probably next up would be Space: 1889, at least as a setting. We used other game systems to play in that universe, and from 1989 when the game premiered until about 2010, there was usually a campaign going, at least part time.