You may not know the name, but you know his work intimately if you have spent time with any of Bethesda's games.

Adam Adamowicz was a talented concept artist at Bethesda, and was hugely influential on the artistic direction of Fallout 3. There is a great write-up about Adamowicz at awesome-robo.com about his influence on at least one other concept artist, and the work he produced while at Bethesda. You can also see him talk about drawing for Fallout on one of the documentaries produced about the game in the video below. Adamowicz appears at around 1:28.

Next time you jump into Fallout 3, look around at how awesome everything looks and make sure to think of Adam Adamowicz.