HOTT For Science Fiction is a set of troop types and amendments for use with the popular Hordes Of The Things.
Rules: Science Fiction
Rabbidgerbal’s Super Simple 1PG Sci-fi Skermish Rules
Rabbidgerbal’s Super Simple 1PG Sci-fi Skermish Rules is a set of free wargames rules meant as a 40K replacement.
Yes, that’s really how the author spelled “Skirmish”
Space Fury Easy Starfighter Combat Rules
Space Fury are a set of quick and dirty space fighter combat rules.
One Page Fleets Starship Combat
One Page Fleet is Mike Wikan’s set of free wargames rules for starship combat.
Star Wars Shootout
Star Wars Shootout is a set of free wargames rules for skirmish combat in the Star Wars universe.