MHO, by time periods:

Ancient History

3000 B.C. to the Fall of Rome 455? AD

Aknaton (Pharoah who first introduced the idea of 1 God)
Plato
Aristotle
Julius Caesar
Jesus Christ

Medievel 500 AD - 1500 AD
Mohamed
Edward I King of England (established the idea of Parlement and common law, and basic human rights such as habeaus corpus)
Leonardo Da Vinci

Enlightment
1500-1880
Thomas Jefferson
A. Lincoln
Darwin
Issac Newton
Louis Pasteur


Modern Age 1880-present
Einstein
Adolf Hitler (bad guy, but the consequences of his life is the story of the 20th Century)
Franklin Roosevelt
Gandi
Martin Luther King Jr.