Rule Zero

Rule Zero is supposed to be the most important rule of any RPG or miniature wargame. It's called the "zero-th rule" because it is so fundamental that it comes before even the first rule stated in any rulebook. It's also a meta-rule, so it doesn't really fit into any numbered lists of rules. Good RPGs and miniature wargames will mention it or something like it in the rule book(s), usually something wishy-washy like "these rules are only a guideline." Sometimes this rule is confused with the Golden Rule: "whatever the DM says, goes." Suffice to say, That Guy is not a fan of either of the above.

Definition

Rule Zero: "Roleplaying games, miniature wargames, party games and board games are entertainment; your goal as a group is to make your games as entertaining as possible. If that means breaking the rules temporarily, or permanently as a house-rule, then so be it."

The best advice ever on how to be a good GM.

Citations

D&D

• In Basic D&D in 1980, the book says on the first page:

"Anything in this booklet (and other D&D booklets) should be thought of as changeable -- anything, that is, that the DM thinks should be changed... The purpose of these 'rules' is to provide guidelines that enable you to play and have fun, so don't feel absolutely bound to them."

• In AD&D, the player's handbook has on page 8:

"This game is unlike chess in that the rules are not cut and dried. In many places they are guidelines and suggested methods only."

• Dungeons & Dragons 3e doesn't explicitly state the rules can go hang, but it does have a section for changing the rules to suit your group (DMG, pg 11).
• D&D 3.5 states in several places that the DM can treat any rule as a mere suggestion at any time. Examples: bottom of page 64, Player's Handbook (Access to Skills), and most directly in the DMG on page 6: "Good players will always recognize that you have ultimate authority over the game mechanics, even superseding something in a rulebook."
• D&D 4e also has a section on creating house rules (DMG, pg 189).
• D&D 5e talks about adding optional rules and how the rules are "guidelines" in Chapter 9: Dungeon Master's Workshop (DMG, pg 263).

Warhammer

• Warhammer 40,000 4th edition rulebook has an awesome entry at page 5:

"The most important rule about playing games of WH 40k is to have fun. Now while having fun can often be gained by mercilessly crushing your opponents forces, never ever forget that you are both here to have fun... If you can play nice and treat your opponent with respect and mercilessly crush their forces at the same time, you really are a winner. "

• Warhammer 40,000 8th edition and 9th edition rulebooks have clearly stated rule zero on pages 180 of the 8th edition rule book and 198 of the 9th edition rule book:

"THE MOST IMPORTANT RULE: In a game as detailed and wide-ranging as Warhammer 40,000, there may be times when you are not sure exactly how to resolve a situation that has come up during play. When this happens, have a quick chat with your opponent and apply the solution that make the most sense to both of you (or seems the most fun!). If no single solution presents itself, you and your opponent should roll off, and whoever rolls highest gets to choose what happens. Then you can get on with the fighting!"

• Warhammer age of Sigmar 2nd edition has the same rule zero as Warhammer 40,000 but reworded for the age of sigmar:"THE MOST IMPORTANT RULE: In a game as detailed and wide-ranging as Warhammer Age of Sigmar, there may be times when you are not sure exactly how to resolve a situation that has come up during play. When this happens, have a quick chat with your opponent and apply the solution that make the most sense to both of you (or seems the most fun!). If no single solution presents itself, you and your opponent should roll a dice, and whoever rolls highest gets to choose what happens. Then you can get on with the fighting!"

White Wolf

• In Vampire: The Masquerade, the core book says:

"This is the most important rule of all, and the only real rule worth following: There are no rules. The world is far too big - it can't be reflected accurately in any set of inflexible rules. Think of this book as a collection of guidelines, suggested but not mandatory ways of capturing the World of Darkness in the format of a game. You're the arbiter of what works best in your game, and you're free to use, alter, abuse or ignore these rules at your leisure. "

• MUNCHKIN has "Argue over ALL THE RULES." It's actually quite fun...
• For some reason, Warhammer Fantasy doesn't have a rule zero actually printed in the rulebook. It's there, but not there, as it's the same as 40k's.

GURPS

• Social Engineering has a section titled Throw Away This Book! discussing whether one even needs rules to facilitate roleplaying.

Palladium

TBA

Uno

• In Uno, the official rules do not allow you to stack draw 2 or draw 4 cards. However, the majority of people ignore this rule to make the game more enjoyable as a group.

Werewolf

• In the social deduction game Werewolf also known as Mafia originally only included 2 roles mafia/werewolves and villagers. However, through house rules a plethora of extra roles to spice the game up has been made. these include but are not limited to: The seer/detective, the bodyguard, the hunter/hitman, the witch, the vampires, the tanner, alpha wolf/mob boss, wolf cub, sorceress, and masons.

Secret Hitler

• The social deduction game Secret Hitler is licenced under creative commons (CC BY-NC-SA 4.0). Part of this licence allows anyone to "remix, transform, and build upon the material."

Chess

• If it wasn't for house rules modern Chess would not exist. The original rules of chess differ from modern chess by the following rules: pawns cannot move 2 squares on their first turn, there is no castling, the queen can only move one square like the king, the bishop can only move a maximum of 2 squares but can jump over pieces, there is no en passant. As chess travelled around the world different cultures came up with their own house rules which eventually became standardised which is why we get chess variants like Shogi and Hia Shatar. Some of these cultures invented the same house rule independently like the modern European bishop and the shogi bishop being able to move an unlimited amount of squares diagonally. The most recent adjustment to the official chess rules was in 1974 after Tim Krabbé published a joke chess problem where the solution was to castle vertically.

Monopoly

• In Monopoly a popular house rule is to gain money after you land on free parking. Despite the popularity of this enjoyable house rule it is not included in the official ruleset. Ironically, many "house rules" applied to Monopoly are examples of taking Rule Zero too far; in trying to make the game more fun, they actually wreck the balance of the game and give it its undeserved reputation for being slow and ponderous. One of the key offenders here is ignoring the auction rules laid out in the instructions; whenever a player lands on a property for the first time, if they choose not to purchase it, it must be auctioned to the highest bidder. Many casual players believe this is too cumbersome, but it actually speeds up the game considerably.