Tom’s Ancient Warfare Rules is a set of free wargames rules for the ancient period.
Labyrintus is a set of free wargames rules in which players try to get their team of miniatures through a labyrinth maze.
Marvel Civil War Skirmish is a miniatures-and-cards game based on the airport battle in Captain America: Civil War. It is played on a checkers or other 8×8 board.
The Stars Our Decimation: Voidstriker is a set of fleet oriented starship combat rules. They can be used as a board game, and with miniatures and hexless play.
Some good basic advice on the layering technique for you wargaming miniatures.