Nelson Mandela's autobiography is one of the most gripping, inspiring, unputdownable books I've read.
Malcolm X's one is interesting, although written with a view towards re-ingratiating himself with the leader of the Nation of Islam Elijah Muhammad, whom he was estranged from at the time. It was also written before he had his personal transformation at Mecca, after he which began preaching a 'let's all get along' type message.
The first half of Charlie Chaplin's one is absolutely brilliant, detailing the story of his childhood in the poorest part of London, raised by a single Mum who lost her livelihood as a singer after her voice deserted her and then descended into madness, and then his eventual rise as a performer. The second half is not as captivating, but that tends to happen in autobiographies after the story of the subject's initial struggle is over.
Richard Branson's one is also worth a look, although it suffers from the same problems as Chaplin's.