Wizards of the Coast, WotC, p.n., abbrev. Seattle-based company founded in 1990 by Peter Adkinson; publishes hobbyist games. [GJ1]
Addendum: Best known for the Magic: The Gathering and (formerly) Pokémon collectible card games, WotC acquired TSR Inc., creators of the Dungeons and Dragons adventure game, and Five Rings Publishing Group Inc., creators of the Legend of the Five Rings trading card game, in 1997 (L5R was later licensed back to its creators who had formed AEG). WotC was subsequently acquired by Hasbro in 1999, a move that many gamers believe to have a serious detriment to the hobby. [GJ1]
Addendum #2: In general gamer parlayance, it is often referred to as just "Wizards" or by just its abbreviation, often pronounced as "Wot-see".