Desmond Tutu (from 2007-2013)
From Wikipedia: The Most Rev. Dr. Desmond Mpilo Tutu (born 7 October 1931) is a South African activist and Christian cleric who rose to worldwide fame during the 1980s as an opponent of apartheid. He was the first black South African Anglican Archbishop of Cape Town, South Africa, and primate of the Church of the Province of Southern Africa (now the Anglican Church of Southern Africa).
Archbishop Tutu has been active in the defense of human rights and uses his high profile to campaign for the oppressed. He has campaigned to fight AIDS, tuberculosis, homophobia, poverty and racism. Tutu received the Nobel Peace Prize in 1984, the Albert Schweitzer Prize for Humanitarianism in 1986, the Gandhi Peace Prize in 2005,  and the Presidential Medal of Freedom in 2009. Tutu has also compiled several books of his speeches and sayings.