'Big Head Mode' is a hidden extra in some games, normally discovered through inputting a cheat code. Due to the increase in popularity of awards systems, such as Achievements, Trophies, and Steam Achievements however, cheat code-based extras such as Big Head Mode are becoming less frequent.
Big Head Mode gives a character a massively disproportionate head, whereupon their physical dimensions change vastly. Occasionally, the arms are also increased in size alongside the head. Big Head Mode is occasionally known as 'DK Mode', as this was the name given to it in the Nintendo 64 classic GoldenEye. The DK stands for Donkey Kong, as the characters' proportions are made to resemble that of the Donkey Kong character.
Rainbow Six: Vegas and Rainbow Six: Vegas 2 both include a Big Head Mode in Single Player. In Vegas, it makes the game more difficult, but potentially also more easy due to the fact the full head can be used for headshots. Some 'DK Modes' in games do not have this feature, making headshots and other more precision targeting harder to perform.
Gears of War 3 also features an unlockable Big Head modifier, though only for the Arcade Mode variants of the story (including the DLC story RAAM's Shadow) and Horde mode. The Big Head modifier not only increases the size of all the characters' heads--for both human and locust--but raises the pitch for all the in-game dialogue, too. Cutscene dialogue receives the same pitch increase as well, but the head size is shown as normal.
Rise of The Tomb Raider features a Big Head modifier for its Expedition Mode, which allows the player to replay sections of the main game with a set of customizable alterations. There exists three different variants. One of which has all characters saddled with a big head, another makes it so only Lara's head size is increased, and the final makes it so only the enemy soldiers' head size is increased.
Both Microsoft and Nintendo used the concept of larger-than-life heads for their interactive characters (the Mii and Xbox Avatar). The large heads were selected due to the fact that they seemed more family-friendly, which is the method of advertising that both Nintendo and Microsoft were aiming for with the addition of the two characters. While the avatar heads cannot be increased in size, they were likely selected as their current size due to the fact that Big Head Modes in games generally make things feel less serious.
The Xbox avatars' big heads were eventually deflated so as the avatars have more realistic proportions, however.
Decline in Popularity
It is extremely uncommon for a 'DK Mode' or 'Big Head Mode' in a game to be available in online multiplayer. This is due to the fact that it normally receives negative comments from players who feel it constitutes as an unfair advantage. Big Head Mode in games can allow part of the head to appear through walls and other supposedly solid textures - this is due to the fact the game was never designed to display a larger head than normal, and the larger head can therefore 'clip' through the wall, displaying someone's position in a situation where it would otherwise have been impossible to know their location.
In some more serious shooters, such as leagues in Counter-Strike and Counter-Strike: Source, players are removed from servers for having mods that may aid them in finding the location of other players. These include the infamous 'Big Head Modes', amongst others. Other complaints relate to the ' hitbox' on player models. The hitbox determines whether or not you hit a target or not, and in some games, the hitbox does not change. This means that the head of a target can be extremely large, but only a small region of it will constitute as a headshot. This makes aiming extremely difficult unless a player is very familiar with the location of a character model's head, and is able to consistently put this knowledge to practice. However, when the hitbox grows larger and the whole head becomes a target, it still draws criticism for making headshots too easy. It is not impossible that the frequent complaints about Big Head Modes in games was part of the reason that they are growing less common.