Isuldur’s Bane is the name of a free set of rules for playing Games Workshop’s Lord of the Rings Battle Game.
Rules: Fantasy
Three Plains 15mm Fantasy Wargaming
Three Plains is a free fantasy wargaming system. It also comes with free print-and-play figures.
Brutality Skirmish Wargame
Brutality is a miniatures agnostic skirmish wargame set in a science fantasy realm. You can get a free version at the link.
Kings of War Starter Fantasy Rules
Kings of War is a new set of fantasy rules from Mantic Games, who make some very cool figures. But the rules are non-figure-line specific. And they’re free.
A Spot of Friendly Wizardry Game
A Spot of Friendly Wizardry is a set of free game rules for duels between two wizards.