Warren Buffett passing on purchasing shares of Berkshire's stock when his company's cash pile is sitting at a record high ($325 billion) signifies that one of Wall Street's most ardent value investors is struggling to find a good deal. Berkshire's price-to-book value recently hit levels that haven't been consistently observed since 2008.

Warren Buffett has been selling shares and stacking up cash at a terrific rate, fanning speculation as to why the world's foremost stock picker is pulling his money out of the market. Berkshire Hathaway roughly tripled its pile of cash, Treasury bills ...

But Buffett hasn't lost his enamor with all stocks. The "Oracle of Omaha" has even invested $2.9 billion in one stock this year. What is it -- and is it a no-brainer buy now?