Fight Dice is a set of free wargames rules that uses a neat dice pool system, where the players allocate handsfull of six sided dice to their actions.
Fickle RPG is
a narrative roleplaying and cooperative storytelling game, distinguished by the core dice resolution mechanic which has bluffing, bidding, and meaningful decisions. The game is a universal system that can be played in any genre, such as sci-fi, military, zombies, high fantasy, superheroes, etc. An ongoing campaign can be played over multiple game sessions, or as a themed one-shot.
Universal Combat System is a set of free wargame srules described by the authors of being for “any number of players in an infinite amount of settings.”
Advanced Wargames Rules is actually a fairly simple set of generic rules
Serious Lemon’s Full Command is a set of free wargames rules:
for simulating battles all the way from a skirmish level with a handful of individual models through to full scale war with units totalling hundreds of miniatures.
Full Command has been designed to be setting and scale agnostic. It can be used to play 28mm skirmishes in an ancient setting to 15mm ranked warfare in a medieval fantasy setting to a 32mm heroic squad based battles in a far sci-fi setting.
Full Command is being released under Creative Commons (Attribution-ShareAlike) to allow maximum flexibility and freedom to gamers everywhere. Always wanted to play that game where Zombie Alien Pirates are battling the Savage Ape-Men on Mars? Grab the core rules, whip up a setting module with a couple of factions and you’re away.