I remember SuSE Linux had a motd that simply said: "Have fun..." That has always been the spirit of Unix, having an environment in which it is fun to work and tinker about. We owe that to Ken Thompson, Dennis Ritchie and their colleagues at Bell Labs (http://www.princeton.edu/~hos/Mahoney/unixpeople.htm).
Dennis Ritchie also evolved Thompson's B into C, giving us a concise and practical systems programming language. Kernighan and Ritchie taught many people how to write great code, some of those people taught other people, directly, or simply by sharing great code. The end result has been a ripple effect that has had a profound and positive impact on how many of us code. Not many people in history have influenced the work of others so much.
Dennis Ritchie is no longer with us, he will be greatly missed. He is among those luminaries we will never forget. The computing community will never forget Jon Postel, Richard Stevens and Dennis Ritchie.Obituaries: