3. Abdullah bin Abdul Aziz al Saud
Country of citizenship: Saudi Arabia
Absolute ruler of desert kingdom that contains the world's largest crude oil reserves, two holiest sites in Islam. State-owned oil producer Saudi Aramco has reserves of 266 billion barrels, or one-fifth of planet's known supply (worth $22 trillion at today's oil prices). Pushing for gradual social and legal reforms, while maintaining good relations with deeply conservative religious establishment. Ultimate succession unclear: 86-year-old king's official heir is 82-year-old Crown Prince Sultan bin Abdul Aziz Al Saud. Established committee of senior princes to ensure smooth transition in the event both become incapacitated.