Certainly Rosa Parks was important to the civil rights movement. Her simple act of not giving up her seat on the bus was the catalyst for change in Montgomery, Alabama. She was within her rights, sitting in the "black section" of the bus. But when the white section filled up, the bus driver told her she'd have to give her seat to a white passenger who had just gotten on the bus. She refused, and she was arrested. Led by the young Rev. Martin Luther King, Jr., black people boycotted bus service and almost bankrupted the company. It wasn't long after that bus segregation was banned.
You might also consider Medgar Evers. Read about him at this site:
I would have to say Martin Luther King Jr. He came out as a simple preacher with a loud protest about the injustice against African Americans. He was a great orrator and very charismatic which is the prefect combination to issue change. He had such a honest truthful song to sing when he spoke, and he spoke to all races. What was brilliant about this man was that he was able to bring black and white races together to fight together for one cause. Martin Luther King Jr. saw a real brotherhood in America, and he is one of the most important people in American History. He is up there with your George Washington, Abraham Lincoln, FDR, and JFK.
The most important civil rights activist of the 1960's was Martin Luther King, Jr. He first came to prominence during in 1955 when he organized a protest in support of Rosa Parks, a black woman who was arrested in Alabama for refusing to give up her seat to a white man on a Birmingham bus. He helped organize a bus strike that finally resulted in black being able to sit where they wanted to on public transportation. By 1962, he worked out an agreement with the Justice Department that abolished separate drinking fountains, sitting rooms and lunch counters for Blacks. In 1963, his march on Washington D.C. resulted in 250,000 people listening to his "I Have a Dream Speech. In 1964, King became the youngest person to ever be awarded the Nobel Peace Prize. He continued his activism until the day he was assassinated in 1968 in Memphis, Tennessee.