The 2008 TIME 100

As Dan Quayle knows, a single event can define one's image. business execs have the same problem. Throwing a chair across the room when an employee tells you he's going to work for a competitor, dancing like a monkey at an employee meeting, screaming "Developers!" 14 times while drenched with sweat at a software conference—things like that are hard to live down. In Steve Ballmer's case, however, it's not a single event (he denies throwing the chair, but the dancing and screaming live on in viral video), nor does it unfairly define his image.

My interview with him onstage at a Microsoft conference in March wasn't exactly soft and lacy. For crying out loud, he threw my MacBook Air on the ground. The man is truly WYSIWYG—what you see is what you get—maybe more so than Microsoft's products. By contrast, Ballmer's title—chief executive officer—is a disguise. He is actually Microsoft's combative, take-no-prisoners chief warrior. If you want 95% of the wallets of every market that you're in, then you want this Steve. If you want 95% of the mind share of every market that you're in, then you need the other Steve (Jobs).

Ballmer, 52, is worth $15 billion, which makes him one of the world's 50 richest people, but he hasn't forgotten what got him there: sheer force of will. Many execs throw fits, dance like nuts and scream, but none deliver results the way Ballmer does. In the past two years, Microsoft profits have surged 20% and sales 28%. He has amassed a war chest, and he has never been shy about deploying it. Yahoo! is learning what it's like to be in his crosshairs. He also swears that he's going to smoke Google. Whether you like the company or not, give credit where credit is due: Steve Ballmer kicks ass.

Kawasaki is the co-founder of Alltop.com and Garage Technology Ventures and former chief evangelist of Apple