Blades of Bronze is a set of free wargames rules designed for short skirmish 15mm ancient wargames. The rules revolve around the ability of the leaders to give orders to the troops.
skirmish
Seventh Spell Fantasy Skirmish Game
Seventh Spell is a set of free wargames rules for fantasy skirmish games.
Fireteam II Modern Skirmish Rules
John Armatys offers a set of free modern skirmish wargames rules called Fireteam II They’re designed for use with 20mm figures.
Point Blank Skirmish Rules
Point Blank is a set of free wargames rules where the units are fire teams and squads. Soldiers are represented individually.
Knights and Knaves Medieval Skirmish Rules
Once available as a commercial rules set — and a nice one it was — Knights and Knaves now is available as a download. Also available are the More Knights & Knaves and Castles, Cogs & Chevauches expansions.