Reaper is giving away its Cowboys and Gunslingers rules set.
Rules: 19th Century
Law of the Gun Wild West Rules
Law of the Gun is a set of free wargames rules by Richard Bradley for Wild West Skirmishes.
Away Boarders War of 1812 Great Lakes Naval Rules
Away Boarders is a neat little game for a little-considered theatre of war: The Great Lakes in the late 18th and early 19th centuries. The author also includes some nice 2-D paper models of the ships, as well as counters.
War of the Triple Alliance Rules
Natholeon’s Empire offers a set of free wargames rules for the War of the Triple Alliance.
The War of the Triple Alliance, also known as the Paraguayan War, was fought between 1864 and 1970 between Paraguay and the Triple Alliance of Argentina, Brazil, and Uruguay. Percentage-wise, it was one of the most devastating wars in history, with Paraguay losing 70% of its adult male population.
Wild West Shootout
From Gettysburg Gamers: a set of free wargames rules for Wild West shootouts.