Plastic Hell is a set of free wargames rules for playing games with bags of dollar store plastic figures.
Three Inch Glory is a set of free wargames rules for battles with Playmobil figures. The games are set in the 18th Century.
Here are a set of rules for playing Calvinball, from the legendary comic strip Calvin and Hobbes. The rules come with figure cut-outs.
d12 Death Blow is a set of rules for man-to-man combat:
d12 Death Blow pits two combatants against each other in a contest for supremacy. The opponents might be martial artists, wizards trading bolds of eldrich energies, mentalists in a psychic contest or a pair of intergalactic wrestlers vying for the Cosmic Championship.
Here are a set of Very Simple Generic Miniatures Rules.