Angel Barracks offers KR 16, a set of free wargames rules for 6mm science fiction skirmishes.
Rules: Science Fiction
Knight Models’ Marvel Universe Rulebook
Knight Models offers its Marvel Universe Rulebook free for the downloading.
Genestealer Cult and Space Marine Chapters For 1 Page 40K
One Page 40K is a simplified version of the seminal miniatures wargame. The rules now offes data for Space Marine Chapters and Genestealer Cults.
One Page Kill Team
One Page Kill Team is a set of free wargames rules for small scale skirmishes in the 40K universe.
Free Dust 1947 Rules
Dust Models offers a free digital version of their Dust 1947 rules.