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.
Dead Simple Steampunk is a set of one-page RPG rules for settings in a Victorian science fiction setting. There’s also a one-page setting and one page for equipment.
Searchers of the Unknown is a set of free role playing rules. These are one-page, minimalist rules, each of which is designed as a stand-alone product. The collection includes: Searchers of the Unkown, Dwarven Glory (and supplement), Karry on Krawling, Witches of N’kai, Adventurers!, Cyborg Samurai Are Go!, Dirty Rotten Scoundrels, Funkin Fists of Fu, Jung Guns, Raiders of the Unknown, The Bastards, Brickmasters of the Unknown, Mutant Got Gunz, Mutant Scavengers of the Ruined Earth (and supplement), Tempora Mutantur (and supplements), Searchers in Spaaaace!!!, Scavengers & Spacewrecks, Swashbucklers of Mars (and a supplement), and Song of the Symbi.
I loved Space: 1889. The setting was fantastic, and I also liked the RPG system. But for those who prefer a more nuts and bolts operation, you could try this GURPS conversion for Space: 1889