Border Reivers were raiders along the Anglo/Scottish border from the 1200s to the 1700s. Here’s a set of free wargames rules for playing out these skirmishes.
Rules: Pike and Shot
Koku Samurai Warfare Rules
Koku is a set of basic Samurai warfare rules with a mechanism for purchasing your troops.
Freebooter’s Fate Free Quickstart Rules
The publishers of Freebooter’s Fate, a commercial set of fantasy pirate rules has released a free set of quickstart rules.
A Splendid Victory ECW Rules
A Splendid Victory is a set of free wargames rules for the English Civil War. They’re designed for 28mm figures, but the basing system is flexible.
Richard Bradley’s Samurai Skirmish Rules
The prolific Richard Bradley has a set of free wargames rules for samurai skirmishes.