This is the primary reason Buffett is dumping Apple stock: He wants to realize as much of a gain as possible by capitalizing on the low tax rate. He also stated that Apple will likely remain one of Berkshire's largest positions.

Buffett doesn't mind sharing his investment philosophy, and comments regularly about his commitment to quality companies over the long term and his general belief in these companies -- through both bull markets and bear markets.

Buffett's biggest purchase last quarter was in Occidental Petroleum. Berkshire Hathaway owns a whopping 27.25% of Occidental's outstanding shares, making it the largest shareholder by far in the company.