10: Abdullah bin Abdulaziz Al-Saud

Oil is power, pure and simple, and nobody controls more of it or has a greater influence on its price than the Saudi king. His country has a quarter of the world's proven reserves, and while other producers might try to drive prices up by withholding supply, Saudi Arabia is the only one that can turn on the tap and drive them down. For now, Abdullah's policy is to restore stability to a market that speculators took beyond even his control in mid-2008. With demand falling dramatically, he'll need to work fast.