10. Procter & Gamble

P&G is the world’s largest consumer product company. Its broad array of products ranges from razors to soap to skin care.

(credit: DANIEL MIHAILESCU/AFP/Getty Images)

9. AT&T

AT&T is one of the largest telecom companies in the world.

(credit: Etienne FRANCHI/AFP/Getty Images)

8. Berkshire Hathaway

Warren Buffett’s (pictured above) conglomerate owns everything from railroads to newspapers to insurance companies.
(credit: JIM WATSON/AFP/Getty Images)

7. Walmart

The world’s largest retailer.

(credit: FREDERIC J. BROWN/AFP/Getty Images)

6. Google

The company still dominates the search engine market.

(credit: Sean Gallup/Getty Images)

5. Chevron

Chevron is essentially a smaller version of Exxon.

(credit: Justin Sullivan/Getty Images)

4. IBM

IBM is to enterprise computing what Microsoft is to personal computing.

(credit: ODD ANDERSEN/AFP/Getty Images)

3. Microsoft

Microsoft was the No.1 company by market cap a decade ago. It's now No. 3.

(credit: TIMOTHY A. CLARY/AFP/Getty Images)

2. Exxon Mobil

Exxon is the world largest oil company.

(credit: Scott Olson/Getty Images)

1. Apple

Apple has become the most valuable company of all time, surpassing Exxon Mobile.

(credit: Spencer Platt/Getty Images)