John McCarthy, creator of the LIP programming language, which went on to become the programming language of choice in  the AI community, and coining the term “artificial intelligence.”  His early work helped shape the direction of AI research basically ever since people began exploring the concept of artificial intelligence.  In 1971, he was awarded the Turing Award from the Association for Computing Machinery for his work with the AI community, and also won the National Medal of Science in 1991.