Some good ones i can think of: cure AIDS, co-captain of the 1992 olympic dream team, nobel peace prize, managing consultant for McKinsey.
Ok in all honesty though... i agree with everyone else, go for quality over quantity. Stick to a couple things that you really enjoy. Some examples might be: YMCA, Boys and Girls Club, Local library, Habitat for Humanity, Nursing homes, Hospitals, Soup Kitchens, Cancer Walks, Little League Coach, etc
Just pick something you enjoy doing and stick with it. Leadership things are pretty difficult to seek out. Clubs are a good way, but usually you have to be an active member for a while to be considered for leadership. Organizing and carrying out a fundraiser or charity event can be good. Examples: blood drive, can food drive, coats for the homeless, emergency cell phones for womens shelter, disaster relief... i have seen all these done very effectively.