Age: 72
Occupation: Supreme Leader of Iran
President Mahmoud Ahmadinejad may make scary pronouncements, but he's not important. Iran's decisions on its nuclear program and all other matters of national security are in the hands of the clerical Supreme Leader. And the fact that Ahmadinejad recently challenged Khamenei's authority and lost has marginalized him even further. As Western powers launch new talks with Iran amid escalating sanctions and threats of war from Israel, resolving the crisis will depend heavily on the intentions of Khamenei, who despite some encouraging noises is keeping his cards close.