Mikheil Saakashvili, President, Georgia (Age: 40)
Dmitry Medvedev, President, Russia
Some people look at these young pit bulls and see George Bush and Vladimir Putin holding their leashes. But in August the two leaders showed that they're not yet housebroken. First West-leaning Mikheil Saakashvili slipped his collar and sent tanks into the breakaway region of South Ossetia. Then Dmitry Medvedev, Putin's handpicked successor, invaded the region with some 15,000 Russian troops. The showdown pulverized Georgia, brought the oil-rich Caucasus region to the brink of all-out war, and pulled the United States and Russia into a tense standoff full of Cold War rhetoric. The barking continued: Saakashvili said an "existential threat hangs over Georgia" and Medvedev boasted that "Russia is a nation to be reckoned with from now on." The stakes are high, says Charles King, a professor at the School of Foreign Services at Georgetown University: "Georgia has been one of the largest recipients of U.S. political and economic assistance, and if it becomes a member of NATO, an attack on Georgia's capital, Tbilisi, would be the equivalent of an attack on Tampa or Tucson." That's why Washington is hoping Saakashvili and Medvedev just learn to heel.