Not sure if this is already known, but it looks like ArenaNet use Blender at least for concept art for Guild Wars 2. The first 15 or so mins of this new Expansion Preview video shows Photoshop and Blender being used.
Have to say GW2 is very pleasing MMO game with a bit outdated but still very nice graphics. Good to know they are using our beloved blender. 
Very nice, even if i am out of mmorpg world, it is good when this kind of publicity shows blender, will draw more people to blender community.