Back in the early '80s, TSR branched out from D&D into other genres - Star Frontiers for Sci-Fi, new editions of Boot Hill and Gamma World, Marvel Superheroes, Top Secret for Espionage, and Gangbusters for 1920s crime in the vein of The Untouchables. Although I owned it, Gangbusters was the one I never actually played or ran, presumably because by the 1980s the cops & robber thing was sort of passe.
It featured a fairly simple d100% system, with 4 ability scores and a few derived ones, like hit points and driving skill. It had levels, and you could spend XP to improve ability scores and gain skills (which were also d100% based). It sort of had classes in the sense that characters had a job and some of these had some special abilities.
