Dennis Ritchie
Father of C & Co-Creator of Unix
"Unix is simple and coherent, but it takes a genius (or at any rate, a programmer) to understand and appreciate the simplicity."
Over four decades of his life, Dennis Ritchie made many lasting contributions to the world of computing. He is most well-known for co-creating the Unix operating system with Ken Thompson. It was while he was working on Unix that he created the C programming language. Both of these technologies and their descendants are widely used to this day.
The C programming language is an improvement on another language that he and Ken Thompson worked on together, which Dennis Ritchie referred to as "Thompson's B". Dennis' improvements to B included new supported data types, and new syntax.
Fun fact: In 1989, Dennis teamed up with the magic duo Penn & Teller and Rob Pike (Who worked on Unix as well as the Go programming language at Bell Labs, among other things) to play a prank on then Nobel Prize laureate and VP of Bell Labs Research Arno Penzias. The video evidence can be seen here: Labscam.