3. Aditya Mittal, Chief Financial Officer
CFO, ArcelorMittal
Despite being the son of ArcelorMittal's founder, Mittal, 35, worked his way up to CFO of the steel company in 2004. He orchestrated the $38 billion takeover of Arcelor, reduced corporate debt, and is helping execute an ambitious expansion plan. Mittal is a well-rounded executive who has the CEO's ear -- and not just because he's a relative.