The 6mm science fiction Yahoo group is very active and has a number of nice rules sets. Maximum Firepower is one designed to be played on a hex grid, and it uses something called the BattleStory system, which it describes as a “universal mechanic that, with the roll of color coded dice, tells you: 1. What orders were issued? 2. How did the troops perform? 3. Who won the battle, and why? 4. What happened to the survivors?
From Baccus miniatures, Old Trousers 6mm is a set of quick-play Napoleonics, played on a 2 foot x 2 foot board.
Mini Nap is a set of Napoleonic Warfare rules for 6mm figures. The authors write:
MINI-NAP is a set of wargames rules specifically designed for playing a reasonably quick corps sized Napoleonic wargame using the 6 mm scale.
They grew out of my desire for a set of rules that would allow two players to play a traditional style, historically based Corps sized game (of around 35 to 50 units on each side) but one that would allow such a reasonably large game as this to be played and finished within about four hours (which they do).
Under the MINI-NAP rules, the basic force normally fielded is a Corps consisting of several Divisions. Unlike many other wargames systems, there is no points system involved in MINI-NAP. Players are encouraged to use an actual historical corps (and historical corps structures). That means you will need to do some research.
As a guide, the MINI-NAP Corps Guidelines give some general details on how many of the various nationalities involved in this period arranged their Corps (and also the Infantry Brigades, Cavalry Brigades, Mixed Brigades, Reserve Brigades and Reserve Artillery of the Divisions therein) and they also include how to rate units. Brigades are important within the game system.
Individual units manoeuvre, fire, fight hand-to-hand combat, etc, during the course of the game by the Brigade, as they did historically. Several Brigades can also manoeuvre by the Division if circumstances allow.
The Dark Realm is a set of free miniatures rules for Dark Realm’s line of 6mm science fiction games.
Germy’s World has some nice paper models for 6mm science fiction gaming. There are tanks, drop pods, a mega drop pod and a drop ship. These would be useful for Battletech, or Reaper’s CAV, or Games Workshop’s Epic 40K.