When Google hired Patrick Pichette as its new chief financial officer in 2008, tech analysts giddily recounted the $1 billion in cost savings he had just generated at BCE Inc., parent of Bell Canada. He hasn’t disappointed, wringing millions in savings from the free-spending tech giant. But what many overlooked at the time was how well-rounded Pichette really is, to such an extent that this spring CEO Larry Page asked him to oversee Google’s (GOOG) business operations and human resources as well.

The story confirms what CEOs already know: A great CFO is his best secret weapon. Increasingly complex financial tools, greater international competition, and the global financial crisis have demanded more from financial officers. A great CFO needs to be part numbers whiz, part general manager, and part consigliere. “Being a CFO means that the CEO can walk into your office and get guidance on almost anything,” says Michael Useem, professor of management at the Wharton School.

Fortune is asking what makes a great CFO as we scan corporate America to pick our Executive Dream Team — our fantasy roster of corporate all-stars. Here are the traits top CFOs possess.

They are great general managers.

Today’s CFO often needs an understanding of the hundreds of fiefdoms within multinational corporations. The CEO wants a new $50 million marketing campaign by next quarter? Okay, how does that change HR’s budget? How about operations? It’s little wonder 21% of current S&P 500 CEOs are former CFOs, according to search firm Russell Reynolds.

They have great external-relations skills.

CFOs need to produce financial results that please lenders, regulators, shareholders, even the IRS. Great CFOs avoid infractions and help keep their company’s stock up. Goldman Sachs’s (GS) reputation has taken a hit since the financial crisis, but no one has questioned the firm’s earning statements, and the stock has rebounded to pre-2008 levels. That’s a credit to CFO David Viniar, who helped steer the investment bank through the downturn.

They can manage complex mergers.

M&A is part of most growth strategies, and it is often up to the CFO to make the marriages happen. Aditya Mittal, then CFO of Mittal Steel (MT), fought off a poison pill and a Russian rival in the hostile $38 billion takeover of European rival Arcelor. The combined company now enjoys scale advantages that no other steel giant can match.

Don’t expect to read about green eyeshades when we announce our dream CFO later this year — fast-moving markets are demanding much more.

This article is from the July 25, 2011 issue of Fortune.

[polldaddy poll=5244216]