It is safe to say that there is not one person in Outliers who is more important than any other. I do however have a few people in mind who I believe made a relatively large impact. These people are Bill Gates, Chris Langan, and Renee.
Bill Gates is obviously the founder of Microsoft but his story goes much deeper than that. From a fairly young age, Gates has had an obsession with computers and programming. He was also born in 1955 which was "the perfect birth date" according to Gladwell. This was the perfect birth date because he was born in the perfect window of the introduction of computers. In addition, because of his obsession, he proved true the 10,000 hour theory. Bill Gates was important because the represented the work ethic of 10,000 hours and success with opportunity (his birthday).
Chris Langan is quite possibly the smartest man of all time. IQ wise anyways. His IQ is 195, that is 45 points higher than Einstein's! Chris Langan was that rare case in which it seemed that he was just born smarter than everyone else. However, with all of this potential he is relatively unknown. His work won't get published because he doesn't even have a college degree. This is due mainly to the fact that he can't get along with others. That is the "problem with geniuses". Despite his intelligence, he is unable to communicate with people in an effective way. I feel that he is an important person because he illustrates that fact that even though a person can be insanely smart, one must be able to interact with others.
The final person is Renee. Initially she has no real interest in math. She then gets her hands on a graphing program on the computer. For 20 minutes she tries to find the slope of a vertical line. Most high school students know that the slope is undefined. She however does not and works to find the answer. She tries various scenarios until she finally realizes that the slope would be infinity over zero. This may seem like a minor achievement but I see it as a breakthrough. This event with Renee shows that with hard work, one can achieve what they set their mind to.