Игры часто демонстрируют то, что приянто называть emergence - появление сложного из простого. Часто игроки умеют обнаруживать в игровой механнике вещи о которых не задумывались сами создатели игр. Иногда это просто фан иногда способ "обмануть игру" и получить серьезные преимущества (exploits) ...

В Deus Ex мины можно вешать не стены и таким образом создавать лестницы - преодалевать стены, которые по мнению разработчиков были неприступны. Это в совю очередь дает возмоджность проходить игру гораздо быстрее...

В 2005 году игроки WOW случайным образом открыли будущие зоны игры (которые планируется запустить только через год) - Caverns of Time, Emerald Dream...

As with all massively multiplayer online games, World of Warcraft has had its share of players who exploit the world of Azeroth. Such abuse ranges from gold farming to selling accounts on eBay. One common exploit was the use of leet (example: |-| () \/\/ |2 U? (how are you?) ) to communicate between the Horde and the Alliance, since symbols and numbers were left unmodified in otherwise scrambled communications. This has since been stopped by modifying the linguistics engine to remove punctuation and numbers from the text.

Speed Hacking/Teleporting/Subterrain Travel - Since character position in World of Warcraft is determined by the client side, it is possible for players to send out artificial positional data and be instantly transported to any part of the world (even underground) or used to speed up traveling speed by increasing positional deltas.

Botting - A player who runs a third party program to control their character. The bot will kill monsters, loot gold, mine ore, collect herbs or gain levels automatically without the player having to be in front of the computer.

Duping - Duplicating, or replicating items or gold

Game Mechanics Exploits / Bug Exploits - There are also other exploits involving the physics of the game, sometimes in conjunction with items. This includes using wall-walking to get into unfinished areas or abilities like the Sentry Totem to make one's character unattackable by other players. These exploits are usually not discovered right away and are allowed to be used (though typically thought of as unfair) until stated otherwise by Blizzard.

Data Mining - This is typically most common around the time that a patch is released on the public test realm. Players will try to access files not yet in game and then host them on websites to expose content not yet released (usually new zones, items, and graphics).

http://www.wowwiki.com/Exploit

Читеры - это совсем другая история
Ставший для многих символом читерства код IDDQD - из игры DOOM

Коды публикуются и существуют специальные программы для мини-хака игр

ArtMoney can make a troublesome game easier to win by helping you find the memory address where a desired quantity (like amount of money) is located so you can change that quantity. In spite of its title, ArtMoney actually allows you to change any quantity specified in a game, whether it be dollars, bullets, swords, or health points. The program finds a hex address based on the input parameters you set and prints these addresses with their corresponding values. For example, if your character has 1,431 dollars, ArtMoney searches and displays all memory addresses containing the value of 1431. Of course, as there can be hundreds of memory addresses displayed after a simple search, you will need to sieve this addresses. You lose nothing if you download FREEWARE Edition of this program.
http://www.artmoney.ru/