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.
Mobsters is a set of roleplaying rules for 1920s gangsters. It’s a well-done and complete game.
Fickle RPG is
a narrative roleplaying and cooperative storytelling game, distinguished by the core dice resolution mechanic which has bluffing, bidding, and meaningful decisions. The game is a universal system that can be played in any genre, such as sci-fi, military, zombies, high fantasy, superheroes, etc. An ongoing campaign can be played over multiple game sessions, or as a themed one-shot.
Tombstone is a free RPG set in the wild west. It’s designed to be rules-light, and has quick play character creation to get you started.