Fanboy

A Fanboy (or 'fangirl', though the feminine term can carry a slightly different meaning) is someone who is considered to be obsessed with something to the point of defending its every flaw and even going into denial when they are proven wrong.

Meaning
Fanboys are most commonly associated with gaming forums, though they can be found practically anywhere where opinions can be cast. Such people are usually fans of on particular mainstream gaming company (Nintendo, Sony or Microsoft), but fans of particular consoles (e.g. XBox 360), series (e.g. the Final Fantasy series) and even individual games (e.g. The Legend of Zelda: Ocarina of Time) can also be applied to the term. Fanboys are usually loyal to just one thing, and react aggressively towards others; for example, a fanboy of Nintendo may make crusader-like offences against Sony and Microsoft (e.g. "the PS3 costs too much"). The fanboy will also go to extremes to defend their own favourites when their flaws are pointed out, and will refuse to accept criticism, often going into denial whilst making childish insults to both the 'attacking' parties and other companies/consoles/games.

It is generally believed that the best way to deal with such a person is to ignore them, as there is really no way to make them appreciate other people's opinions.

Traits
Fanboyism is more-often-than-not associated with gamers in early adolescence (ages 12–14 approximately), though it can apply to anyone of any age. Fanboys found on Internet forums are often known to make poor use of English grammar, some even spamming in 1337. They take the pointing out of flaws or negative opinions towards their favourite system or game very personally. They will boast the good pros of their favourite, and either deny the cons, or make invalid arguments against them.

Fangirls
Although females aren't as common in the field of fanboyism, fan'girls' certainly exist. However, the term 'fangirl' is more often self-proclaimed. Fangirlism is often no more than the strong support of a game, or a male character from a game, whom the girl may be romantically or sexually attracted to without any competitive aggression. Whilst a fanboy is associated with one who doesn't respect the opinions of others, fangirls are less likely to attack opposers or react aggressively when attacked.

Attractive male characters in video games are prone to receive many so-called 'fangirls'; girls who admire or are attracted to them. A devoted fangirl is stereotyped to write fan fictions about their favourite game or character, and publicly announce their passion through the use of forum avatars and signatures.