Space Rat is an RPG written by Nathan Russell in just 24 hours. It’s inspired by the cheesy science fiction movies of the 70s. It looks like a lot of fun.
Dark City Games’ Legends of the Untamed West is a tactical RPG for the 1800s American West. The system is based on the wonderful Fantasy Trip system that originally was published in the micro games format. If you’re familiar with the Fantasy Trip, you know that it makes for just as good a miniatures system as an RPG.
You can’t get the Fantasy Trip any more, but you can get Dark City Games’ Legends of the Ancient World, a free tactical RPG that uses the same mechanics.
Labyrinth Lord is a free “throwback” style RPG.
I’m old school, so I’m going to give this a serious look.
RPG Now has a free horror RPG module called Dead of Night: Night of the Santa Claws. It’s designed for the Dead of Night RPG, but no doubt could be modded for any other system.