Basic Roleplaying is the core roleplaying game system used by the small publishing company Chaosium, Inc. It's a simple, intuitive system, with no classes or levels. The game system has been used for RuneQuest, Stormbringer, ElfQuest, Worlds of Wonder, Nephilim, Call of Cthulhu, and many other roleplaying systems. Chaosium is now releasing their Basic Roleplaying system again, as a generic d100 roleplaying system - capable of running anything from fantasy to sci-fi to superhero games.

The Complete Omniversal Roleplaying System from the Blacksburg Tactical Research Center -- or CORPS from BTRC for short. A universal game for any setting based on human norms, with detailed combat rules.

A roleplaying system derived from Dungeons and Dragons and released under an Open Gaming license (similar to Open Source software licenses) to encourage the creation of compatible games.

Free pen-and-paper roleplaying games designed to be used in a variety of gaming genres.

FUDGE, the Freeform, Universal, Do-it-yourself Gaming Engine, is a roleplaying system designed by Steffan O'Sullivan and published by Grey Ghost Games in 1995. Flexible mechanics and generous licensing agreements have contributed to the use of FUDGE rules in a variety of genres.

Fuzion is a "meta-system" (developed from R. Talsorian's Interlock and Hero Games' Hero System) that allows gamemasters to customize the rules for specific genres through the use of modular rules "plug-ins". Generous licensing rules (and free downloads of the core rules) have encouraged the adoption of Fuzion by many commercial and noncommercial game designers.

Steve Jackson Games' Generic Universal Role-Playing System is a skill-based universal RPG with no random elements in character creation. Supported by a large library of published sourcebooks in every imaginable genre, GURPS is a popular choice for do-it-yourself Game Masters.

Hero Games' Hero System was the first universal roleplaying system, predating GURPS by several years. Characters are designed with points spent on characteristics, skills, and powers, and gotten from disadvantages. Powers are generic and effect-based -- combinations of advantages and limitations are meant to produce any conceivable playable effect. The Hero System began with its most popular member, the super-hero game Champions, but also includes Danger International, Espionage, Fantasy Hero, Justice Inc., Robot Warriors, Star Hero, and Western Hero.

Palladium Books' game set on a future Earth where the psychic energy released by casualties of a nuclear war has opened rifts to other worlds, allowing bizarre and powerful creatures (including characters from other Palladium games) to invade.

A card-based roleplaying game published by Wizards of the Coast.

A dice-based rules system used by Dream Pod 9 for most of its roleplaying line.

Torg takes place during the Possibility Wars, when extradimensional High Lords have invaded and transformed portions of the Earth into 'cosms' representing different gaming genres. Torg was published in 1990 by West End Games, then briefly licensed by Omni Gaming Products before going out of print.

Guardians of Order's "cinematic" multi-genre system, used mostly for games based on licensed television and movie characters. All Tri-Stat games share a basic mechanic (based on three character ability scores: Body, Mind, and Soul), adding additional mechanics as necessary to fit the game setting. As of October 2000, the Tri-Stat games are Big Eyes, Small Mouth, Demon City Shinjuku, Dominion Tank Police, Ghost Dog, Sailor Moon, and Tenchi Muyo.