Nights of the Crusades is an RPG that’s gotten lots of good reviews. The good news is that the pdf is free.
Role Playing Games
BioSyndrome Zombie Survival Horror Game
BioSyndrome is a community created game of zombie survival horror.
Hulks and Horrors Science Fiction RPG
Hulks and Horrors was an unsuccessful Kickstarter effort, but now is available as a free pdf.
Dungeon Quest RPG
Dungeon Quest is a free old school fantasy RPG.
Verge RPG
Verge is a free RPG that bills itself as “Fantasypunk.” It’s set in a vast and ancient city.