Swords & Wizardry Core Rules (S&W)
The Swords & Wizardry rules are extremely short, compared to the multi-paged rule-libraries required to play most modern role-playing games. Yet this game contains within itself all the seeds and soul of mythic fantasy, the building blocks of vast complexity, the kindling of wonder. "Edition Zero" is so powerful because it's encapsulated in a small formula, like a genie kept imprisoned in the small compass of an unremarkable lamp. Take this framework, and then imagine the hell out of it!