A GameSystem that can, in theory, be used to play a game in any setting.

Universal systems are good in that if you want to switch genres you don't need to do much more than the standard preparation for a new game. You already know pretty much everything you need to about the rules.

However, universal systems in practice tend to be better at some things than others. This is especially true if the system was not originally designed as a universal system but grew into one over time. In particular, a number of 'universal' systems -- especially the more complex ones -- turn out to support [[HumansAreAverage basically]] ''[[HumansAreAverage human]]'' [[HumansAreAverage characters]] best and increasingly break down the further a character or creature is removed from that default assumption. (Obviously, this is mostly a problem for groups trying to play in more fantastic genres like comicbook superhero action or, well, fantasy.)

Some universal systems are also generic, meaning they can be used to play any style of game, from near-freeform roleplay, to fantasy dungeon crawling, to equipment-focused tactical play involving tons of preparation. The difference here is not in the subject or setting of the game, but in what the players have to do in order to play it. This type of GameSystem needs to have a lot more rules than any particular game played with it will need, so generic systems will usually be "modular," meaning that optional rules can be easily added and removed from the game as it is convenient to do so. It usually isn't possible to design a game so that ''none'' of the rules are mandatory, so generic {{Game System}}s conventionally have a small set of rules designated as "core" rules. These are often distributed separately from the optional rules, sometimes in multiple versions of varying depth; for instance, the sixth edition of HERO offers a "lite" edition for free, a Basic edition in softcover that omits the more esoteric options, and the full rules in hardcover.

{{Tabletop RPG}}s in general have been using Universal Systems more often in recent years, and many game designers who are designing a system from scratch for their particular setting will nonetheless give it some qualities of a Universal System, such as simple, general task-resolution mechanics, and combat systems that work the same regardless of the particular actions the combatants take. The system in question might never be released as an independent system, Universal or no, but the same things that make a system Universal also make it easy for {{Game Master}}s to use the system in precisely the way they want to. {{Game Master}}s tend to like this.


* ''Basic Roleplaying'' (TabletopGame/CallOfCthulhu)
** Pros: Uses percentile dice, meaning you can easily tell what percent chance you have of success for any given roll; easy to learn.
** Cons: Limited material.

* ''D6 System'' (''{{Star Wars}}'', etc.)
** Pros: Simple, adaptable core mechanics; easily learned and customized; available free under SRD; low gratuitous complexity, meaning little maneuvering room for munchkins. Works for almost any setting.
** Cons: Skill advancement has never really worked; the scaling system sometimes produces strange results; [[http://opend6.wikia.com/wiki/File:Contribute.jpg feels samey]]. Makes almost any setting feel like TheThrawnTrilogy, so not truly "generic". Little support compared to GURPS and d20.

* ''D20'' (''{{D20 Modern}}'', ''[[{{Dungeons And Dragons}} Dungeons & Dragons]]'', etc.)
** Pros: Sheer number of books (especially fantasy ones), most famous game on the market, easy to make a character, easy to guess approximate odds of success. Core system free online.
** Cons: Level-based system, mostly fantasy. Lends itself to being broken, as it's almost always possible to get enough bonuses to make important rolls trivial. Often uses multiple dice of varying sizes.

* ''Fate'' (''{{Spirit of the Century}}'', ''{{The Dresden Files}}'', ''{{Strands of FATE}}'', ''{{Fate Core}}'')
** Pros: More structured than ''{{Fudge}}'' (on which it's based) while retaining freeform elements and adding some fundamental new concepts (notably aspects and the fate point economy); several commercial derivatives covering popular genres available.
** Cons: No two releases share ''quite'' the same system due to evolution, genre-specific additions, and/or licensed publishers' individual takes (a dedicated universal "core" rulebook finally came out in 2013, revising the rules again in a number of ways); fairly elegant system hasn't prevented commercial products from turning into well-intentioned comprehensive doorstoppers; game inherently relies on some "metagame" mechanics (fate points et al.) that may not be to everyone's taste. Many -- though not all -- versions retain the use of Fudge dice (see below).

* ''{{Fudge}}''
** Pros: Freely available, potentially rules-light and intuitive system, highly customizable.
** Cons: Relatively obscure with little explicit support; default resolution mechanic based on special "Fudge dice" (effectively just d3-2 each, but official product can be hard to find); customization all but ''required'' for any but the most free-form play => potentially high up-front preparation workload for the GameMaster.

* ''Fuzion'' (''ComicBook/{{Artesia}}'', ''Cyberpunk v3.0'', etc.): A blend of the ''HeroSystem'' and the "Interlock System" used in ''Mekton'' and ''Cyberpunk 2020''.
** Pros: Got some exposure in anime licenses like BubblegumCrisis and DragonBallZ
** Cons: Very difficult to expand into settings that didn't have official support; system is largely dead due to lack of continuing support

* ''{{GURPS}}''
** Pros: Sheer number of books, very well researched, quite internally consistent, tons of skills. All success rolls are against the character's skill modified by the situation, meaning there's no need to arbitrarily determine the number to roll against. All success rolls are on 3d6, giving a realistic probabilistic curve. System is designed to be very modular, adaptable, and customizable, with most rules being optional. Combat actually moves pretty quickly once you get used to it, since a lot of the "standard" modifiers are prefigured. No levels or class restrictions. Basic "Lite" rules free online.
** Cons: A lot of point-juggling (4th edition offers a lot of templates, but they aren't exactly easy to read), 3rd edition vehicle rules. It's easy to get situations with tons of modifiers, bonus ''and'' penalty. Character creation can be very intimidating from the sheer breadth of options and skills, especially without GM help. Balance issues at very high power levels. Not as "universal" as is advertised, as the base system has required new rules added to it for every new genre or setting for it to work.

* ''HERO'' (''{{Champions}}'', etc.)
** Pros: Open-ended, user-defined power system based on effects rather than causes, which provides internal extensibility like a programming language, one can even use the Hero System to simulate other game systems' mechanics. The rules are designed to scale to ridiculously high power levels, while still functioning reasonably well at normal power levels. Lots and lots of optional rules that are ''truly'' optional, so players can fine-tune the "physics" of their game world if they want to. The base rules work just fine regardless of setting or genre.
** Cons: "Big grained" scale, where attribute/base skill rolls only have 4-5 meaningful values within human norms; abbreviation-dense jargon ("4d6 NND EB, 0 END, OAF"); number-crunchy character creation (at least when powers are needed); lots and lots of optional rules ...

* ''Palladium'' (''Heroes Unlimited'', ''Palladium Fantasy'', ''{{Rifts}}'', ''{{Robotech}}'', ''[[TabletopGame/TeenageMutantNinjaTurtlesAndOtherStrangeness Teenage Mutant Ninja Turtles]]'', etc.)
** Pros: Wide variety of material to support the system, much of it produced for the {{Rifts}} game.
** Cons: System suffers from its lack of consistent central mechanics and significant PowerCreepPowerSeep. System creator Kevin Siembieda's stance against posting conversions to or from the system and (to a lesser degree) any original material for the system on the Internet is off-putting for some fans.

* ''{{Prose Descriptive Qualities}}'' (''Dead Inside'', ''Monkey Ninja Pirate Robot'', ''Truth & Justice'', etc.)

* ''{{Risus}}''
** Pros: Speedy character creation, easily-understandable rules. Also, free.
** Cons: Lack of reasonable balance - for the most part, the character with the most dice will always win. Not well suited for serious campaigns, although it's doable.

* WhiteWolf's ''Storyteller/Storytelling'' systems (''TabletopGame/{{Exalted}}'', ''TabletopGame/TheWorldOfDarkness'', ''TabletopGame/{{Scion}}'', etc.)

* ''Savage Worlds''
** Pros: Extra simple, with a slim rulebook that only costs $10.
** Cons: Universal, but not generic--every Savage Worlds game plays like an action movie. Character customization is mostly limited to assigning ranks to skills.

* ''Tri-Stat'' (''TabletopGame/BigEyesSmallMouth'', ''{{Silver Age Sentinels}}'', etc.)
** Pros: It's free, and fairly easy to learn. It's animesque.
** Cons: Not supported anymore, combat's slow. Easy to break.

* ''True20''
** Pros: Based on a simplified d20 system, so most players will already have a grasp of the rules.
** Cons: Powers are BROKEN. Uses a confusing and easily-overpowered damage track system instead of hit points, resulting in odd outcomes - for example, a non-combat-specialist one-shotting extremely powerful enemies because it couldn't see him.

* MutantsAndMasterminds
** Pros: Has a wide range of powers and rules to customize said powers and/or the character itself. The basic books are so devoted to customization that the most of the different books add little new rules and deal mostly to adapt some concepts to a new fiction genre.
** Cons: It is sold as super-hero game, but because of the nature of the super-hero genre it ends up being much more flexible. The GM must keep a eye to avoid game breaking.

* The TabletopGame/LegendSystem
** Pros: Based on the d20 system, and built with balance in mind. The track system and an insistence on letting players and [=GMs=] come up with their own fluff combine to allow you to build literally anything. Monsters are built to the same specs as {{Player Character}}s, which results in loads and loads of abilities flying around during combat. Despite all this, it's a slim rulebook and currently free.
** Cons: As of this writing, it's still in beta and has several GameBreaker elements (with Discipline of the Serpent and the Flurry maneuver standing out as the worst offenders). In addition, as a d20 game, it's not well suited to low powered campaigns at all.

* A few {{Collectible Card Game}}s use the concept of Universal Systems to bring together similarly-themed licenses under a single banner. This list includes the Universal Fighting System (which covers fighting games like ''StreetFighter'' and the SoulSeries), the VS System (covering comic books like those of {{Marvel}} and {{DC}}) and the Crusade System (covering {{Anime}}, primarily HumongousMecha series like ''{{Macross}}'' and ''CodeGeass'').
** Then there's HeroClix, which started with just Marvel and DC, but at this point encompasses a wide variety of franchises, including assorted video games such as GearsOfWar and StreetFighter. Add in Horror Clix (which I believe has compatible rules), and the Clix system will soon enough become as universal as a miniature system could possibly be.

Systems to add:
* ActiveExploits
* GUMSHOE System
* One Roll Engine
* Rolemaster
* UbiquitySystem
* {{Unisystem}}