|RPG published by
TSR's Western RPG. Probably mainly remembered for having a character conversion discussion in the Advanced Dungeons & Dragons Dungeon Master's Guide centered around grabbing modern weapons and explosives and taking them to other settings, as at least one guy canonically did.
Since it focused on somewhat realistic gunplay, it was one of those systems that you'd best not get too attached to your characters, as you might go through three in a particularly bad session. Even if you got lucky enough to survive for a while, there weren't a lot of progression mechanics, meaning you never got harder to kill.