There is one stock he has never sold since buying in 1991, though: American Express ( AXP -0.20%). Buffett owns over 20% of the credit card issuer and bank, making it the second-largest position in the Berkshire Hathaway portfolio. The position trades at a value of $40 billion as of this writing.

Warren Buffett has been on a selling spree and recently trimmed his two biggest holdings: Apple and Bank of America. Buffett caught many investors by surprise when he trimmed his Apple position,

Chubb trades at a hefty price-to-book value of 1.75, which is near the high end of its five-year median. Still, given its record revenue and earnings, robust balance sheet, and shareholder-friendly history, the stock appears deserving of its high valuation.