Games Workshop offers the core rules for its Age of Sigmar Rules free for the downloading.
Rules: Fantasy
Scorched Parchments
Scorched Parchments is a fantasy supplement for the Wars of the Roses rules Torn Liveries. Both sets of free wargames rules are available at the link.
Dungeon Saga Core Rules
Mantic offers its Dungeon Saga fantasy rules free for the downloading.
Elder Scrolls Miniatures Game Rules
Modiphius is offering a free PDF of their Elder Scrolls Miniatures game.
Peep Wars Wargames Rules For Marshmallow Candies
What do you do with all of those leftover Easter candies like marshmallow peeps and jelly beans? Play a wargame, of course. Invisible City Productions has rules for just such a scenario, called Peep War