Quick and Simple Wargames Rules For Everything are just what they say. These would be good for introducing young ‘uns to gaming.
universal
Vortex Universal Miniatures Rule
Unified Theory Game offers Vortex, a set of free wargames rules for a wide variety of periods. They write:
Vortex is an omni-genre customizable miniatures game for two or more players as infinite as the players’ imaginations. Not only is it possible for a Roman centurion, an old west cowboy, a space pirate and a giant cybernetic alligator to meet on the battlefield, they could find themselves on the same team.
Vortex is a fast-paced game that keeps players involved at all times. The rules are easy and quick to learn while still containing vast amounts of diversity to provide for continually interesting play, game after game. A full campaign system is available which makes each game count, and allows the miniatures to change and progress. The players have the power to write their own story in the Vortex universe. A detailed tournament system is also available for those with a taste for short-term competition.
Kings Of The Ring Fighting Game
Kings of the Ring is a set of free wargames rules for one-on-one combats.
GRIT Multigenre Miniatures Rules
GRIT is a set of free wargames rules for nearly any genre. The authors write:
GRIT™ is a system of rules designed for tactical gameplay with 25 — 28 mm miniatures where each figure represents one person or creature. The rules can be used for scenarios where each player employs a single miniature, a tactical squad, or battle groups with reinforcements. Distances are presented in the form of inches with the scale 1″ [2.5 cm] on a table-top or playing surface (if using Adventure Areas™ or other interior gameplay surface this is divided into 1″ squares or hexes), equaling 5′ [1.5 m] — all measurements listed in feet are relative to scale of the miniatures. GRIT may be used for solitary play or for two or more players — a Gamemaster (referee) is optional (employed for ‘double-blind’ games where players only place miniatures on the play area when they are in the Line of Sight of opposing figures).
GRIT was developed in response to a demand for miniatures rules that balance fast setup and gameplay with unlimited Action alternatives and roleplay style Characters that can develop their capabilities. GRIT Scenarios can encompass any genre or time period and make use of any style of miniature figure or terrain element. Victory Conditions, Scenario Complications, and level of realism and detail can be as simple or complex as desired.
Players have the option of basing Characters on a template, an existing roleplay Character, or generating an original Character with unique Stats. Characters can attempt any desired Action, and have the capacity to revive from unconsciousness, heal, and use any weapon or object.