"All of original D&D in a hundred pages — for free."
White Box: Fantastic Medieval Adventure Game is Charlie Mason's ultra-light clone of 1974 original D&D. A reworking of Swords & Wizardry WhiteBox with an added thief, jousting, and travel rules. Free PDF, print-on-demand at cost — small wonder it's called 'one of the most affordable OSR games to play.' A perfect on-ramp into old-school play.
Setting-agnostic classic fantasy: dungeons, villages, dragons. The rules' minimalism makes White Box a clean frame for any world. The spirit is the earliest D&D — imagination over tables, and the GM deciding everything the slim book leaves out.
Single saving throw
Like S&W WhiteBox — one unified saving throw instead of five categories. As simple as it gets: minimal tables, maximal speed at the table.
Four classes
Fighter, Cleric, Magic-User, plus an added Thief. Nothing extraneous — the very chassis of original D&D, easy to bolt your own ideas onto.
Ascending or descending AC
Both armor-class options are included. Compatible with old-school modules and with modern d20 players' instincts alike.
The cheapest full OSR
The complete rules are a free PDF; print is sold at cost on Lulu/Amazon. The whole game fits in ~100 pages. A zero-cost on-ramp into old-school play.
Open in Session Zero to let every player vote and see the results.