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?

Changes in Berkshire Hathaway's stock portfolio are closely watched. Warren Buffett tends to hold stocks for the long term.

It is indeed interesting that Berkshire now holds $320 billion in cash vs just $272 billion in equity investments. Put another way, Buffett is holding more cash than stocks. "That’s a lot of firepower if markets see a sustained drop," notes Colas. "While Berkshire is not especially expensive, its multiple may be worrisome to a value investor ."