Important people in Computer Science

List the names of important people in Computer Science and their contributions to the field. I will start.

Grace Hopper - She built the first compiler named A-0. She is credited with popularizing the term debugging, because she found a real bug (a moth) stuck in a relay therefore impeding the system.

http://en.wikipedia.org/wiki/Steve_Ballmer
As of 2011[update], his personal wealth is estimated at US$14.5 billion, ranking number 46 on the Forbes list of billionaires.
I dunno how you can be more important in CS.