I use it all the time when i need to know something

Yep, especially when I'm stuck on a quest or something. Build section is also very nice. That webpage helps alot.

so true, the /wiki feature is so underused in the game...great feature...
while out of the game, however, the unofficial wiki (http://guildwars.wikia.com/wiki/Main_Page) Flinte posted is my personal preference

GuildWarsWiki is damn useful, and I love that we can access it from in game using /wiki command. Now if only more people would start using it, so it could have the same amount of information as the old GuildWiki.

sometimes its annoying when players in outposts ask questions that can easily be found in both Wikis
all they have to do is press F10 ingame, or type /wiki <subject>
ANET has made it so easy for everyone
i frequently visit the armors page to plan my next elite armor for my chars ^^

Basically my Guild Wars guide to the basics, quests, help and descriptions.

This is the official wiki. While this is good and helpful, it doesn't hold a candle to the unofficial wiki (http://gw.gamewikis.org/wiki/Main_Page).