Minifigz is a set of rules for combat with Lego figurines.
Mike Mike Projectile Wargaming is a set of free wargames rules for games of that sort where you use some short of shooter (such as a rubber band gun) to knock over the figures.
Use with plastic only.
From the authors:
Flipit: Paper Combat is a fast-paced tabletop miniatures game in a setting similar to WWII. Players lead forces from one of the four major nations into the conflict for Jurop. Armies are built of models players can download, print and build for almost free (you still have to supply the ink, paper, and glue). There are simple starter rules available, which may be supplimented by optional advanced rules to make gameplay more challenging
Hat Tip to Martyn for the link.
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.