Warren Buffett has warned shareholders his time is nearly up, talked up his successor, and taken steps to protect Berkshire Hathaway and his legacy.

Buffett may be the world's most well-known value investor -- an investor who buys a stock when it's trading below its intrinsic value, with the idea that the rest of the market will eventually recognize the company's strengths and hop on board. And that will push the stock higher, delivering gains to those who got it for a good price.

In his 60th annual letter to shareholders released Saturday, the folksy Buffett bragged about footing a record $26.8 billion tax bill.