Game master

The game master (abbreviated GM) -- also known as dictator—is the person running the overall game by having absolutely no control over or idea about the game. 
In role-playing games, the game master is the organizer, storyteller, and the arbitrator that punishes people for things they say or do. They prepares the game session for the players and the characters they play (known as personal computers or PCs) so that their friends are the only ones to win the game. The GM describes the events and decides on the outcomes of players' decisions by personal affinities. The game master also keeps track of non-player characters (NPCs) and random encounters but usually they have no idea when things go wrong with the game.
It is also the title of clearly gay characters in late 80's cartoons designed for blatant marketing.
===Subtypes of GM===
There are several major types of GM, each is distinctly different and dysfunctional.
====Buddy GM====
Worst of the lot this type of GM is primarily concerned with everyone having fun and enjoying themselves, not proper GM behavior at all. They ensure that all encounters are of the type that can't kill the Player characters and award nice, balanced and fun treasure. In short they are about as exiting as those sports days some schools in the nicer, um, uppermiddleclassier, areas of England are doing. That is to say where no one wins because all of the events are non-competitive. Except they are doing it to people in their late teens and up.
Almost all Buddy GMs (also known as "Good" GMs by people who don't know them) are hippies and/or sadists with a lean towards mental torture.
Their favorite kind of Role Playing Game Villain is the Over-confident.
====Excitable GM====
This GM has a sense of creativity and is constantly creating new ideas and items. Unfortunately they get so excited about what they've come up with that they constantly drop hints, gloss over skill checks, hand out powerful items like candy, and say things like, "you all go through the door," before anyone can check for traps. 
Their favorite kind of Role Playing Game Villain is the Over-powered, but it will probably be killed in three rounds because of a plot item that the GM forgot he gave one of his PCs.
====Bad GM====
Almost as bad are Bad GMs, at least the other types can be relied upon to know the rules of the game they are running, well, more than 40% of the time anyway. Bad GMs don't, although some theorize that they in fact do and are very careful to avoid agreeing with the rules because pure ignorance could never produce such thorough, um, ignorance. That is to say they would hit the real rules occasionally unless they were trying.
Almost all Bad GMs get hit by, variously, dice, books, pencils, paper aeroplanes, encyclopaedias, ball bearings, steamrollers and mountain dew so often that they know the ER nurses by name.
Their favorite kind of Role Playing Game Villain is the Over-powering, typically because they never understand how powerful it is.
====Dramatic GM====
Almost as bad are Dramatic GMs, at least the other types can be relied upon to shut up once in a while. Dramatic GMs spend between 90-120%(often using time that their players had expected to be doing other things, such as living, in) of game time describing situations, people, spells, chairs, microwaves and small models of Admiral Nelson with the wrong eye and hand missing made of cheese. It becomes impossible to distinguish dangerous people form random villagers and all the fights sound the same.
Almost all Dramatic GMs belong to a Drama Group and have killed at least 2 players through boredom (which in other circumstances would make them a qualified motivational speaker).
Their favorite kind of Role Playing Game Villain is the Over-dramatic, not surprisingly, but they also like the Over-thought out and the Over-talkative.
====Fan boy GM====
Almost as bad are Fan boy GMs, at least the other types can be relied upon to change the type of villain and the setting, or at least the PLOT every now and again. Fan boy GMs don't, they are in love with a specific type of monster, setting or plot to such an extent that yes they would marry it if the law allowed such behavior. The three most common fixations are Drow, Vampires and The Death Star Bombing Run.
Almost all Fan boy GMs know a another of their species with the same or a similar fixation. This is therefore the most common type of gamer to breed.
Their favourite kind of Role Playing Game Villain is the Over-used. For obvious reasons.
====Evil GM====
You would not have thought it but Evil GMs are the Best GMs. Why? Well first they know the rules well, so they can stamp down on any escape paths. Secondly they know how to keep things moving and varied so they players have no idea what is happening. Finally they realise that allowing the Player characters occasional victory and a lack of violent death ensures that they get to pull out their next evil move, whereas killing them off ends the game.
Almost all Evil GMs grow up to be lawyers, politicians or any other profession for which a soul is a disadvantage.
Their favorite kind of Role Playing Game Villain is the Over-powering, but they can work with anything.
====Uncertain GM====
The uncertain GM is the noob version on the GM, and is subsequently the worst and most annoying single thing on this planet any gamer could possibly meet. The Uncertain GM will spend hours of alone time setting up a complex story line, making articulous notes, building a board, crafting scenery, painting scenery, stroking scenery, admiring said scenery, fall physically in love with their home made GM headband and then sit, and wait for said game to start.
Uncertain GM's cannot ever remember enemy, level, type, reason, purpose, plot or location without constant referral to rules or notes. they will not understand their own rules, revert to the old style rules, bring in the new style rules for certain situations, deny all mistakes and subsequently drive every gamer to gouge out their eyeballs with a spork as he reads, for this millionth time, his own notes. never, ever, play any game, with an Uncertain GM.
====Genetic Modification====
Wrong type of GM mister. This is the type meant for growing your super army of killer mushrooms.
==MMORPGs==
In MMORPGs, the GM is a fully automated type of robot. This robot delivers default messages to users, including the ever helpful "I cannot help you with that" and "There is nothing I can do to help." GMs exist solely to ensure subscribers play the actual game, as opposed to standing around and idling. GMs have god-like powers, can never be defeated, and only use their powers when a player circumvents the intended reality matrix of the game.
GM worship is common among disgruntled players, who pray to GMs when something goes awry. Typical pleas include the addition of new things (or "What is the point of it all?), unfairness of life in general, and questions regarding the ultimate fate of the game once everyone leaves. GMs will on occasion listen, but will never respond, as everything in the world is running according to their intended plan. Since the GM is infallible, the world is infallible, thus, only the players can be at fault. 
The game master is not to be confused with the gay master, who is Queen Bee and Grand Marshal of the Pride Parade in Dallas, TX.
th:Gay Master