Bob Cordery’s Bundok and Bayonet free colonial wargames rules are available here. They are a clean, well-written set that use a card activation system. Two things I really like about these rules: 1) that you check morale before moving 2) a bucketsful of dice mechanism for combat.
Miniatures Rules
Prehistoric Pocket Dinosaur Hunting Rules
Prehistoric Pocket is a set of rules fr dinosaur hunting.
Drake: The Dragon Wargame
Drake: The Dragon Wargame is a set of free wargames rules for fantasy wargames focusing on Dragon leaders with their servants and lieutenants.
Andy Watkins’ Vietnam Rules
Andy Watkins offers a set of relatively simple Vietnam War rules.
Duel Blade
A two-player head to head combat mechanic for table-top game play, Duel Blade pits two combatants of equivalent skill in a contest of strategy and endurance. Choice of armor and weapons helps to shape combat strategy and fighting style. Weapons balance attributes of accuracy and power, armor balances the attributes of evasion and deflection. Are you a powerful barbarian brandishing a mighty battle axe, or a swash buckling pirate who finds value in speed over strength? Choice of armor and weapon will change your strategies and your game.
Game mechanic uses 2d6.