PZ8 Sci Fi is a set of free wargames rules for using 6mm (microarmor) figures in a science fiction setting. They’re available on the Yahoo 6mm Wargames Group.
Airland War is the successor to Steve Lorenz’ successful, commercially published Panzer War miniatures wargames rules. The rules simulate modern warfare using microarmor miniatures. You can now get Airland War as a free download.
Tactical Command is a set of free wargames rules for fast play games using micro armor. Scale is 1″ = 100 yards, and each stand represents a platoon of vehicles, men, or towed guns.
A part of the comprehensive PZ8 series, PZ8 1975 – 2010 is a two page set of free wargames rules for 6mm figures.
Threat is a modern micro armor game. The authors write:
THREAT is a modern-era miniatures wargaming ruleset that was designed to be a fast-moving fluid game of modern tactical ground combat using 1/285 scale miniatures.
THREAT is a very realistic simulation of the deadly modern battlefield. Combat is simultaneous, for this reason a referee is recommended to direct resolution of the firing and resolve line of sight (LOS) problems. Each miniature represents a one-for-one ratio of personnel and equipment. Aircraft may represent multiples of aircraft of similar type.
Unlike other game rules, THREAT does not use individual vehicle charts, rather it uses charts for each weapon system that modern vehicles employ. In this way any number of vehicles with different weapons mountings can be utilizied without having to create new charts.