Two historically inexpensive stocks in Berkshire Hathaway's $297.5 billion portfolio are ripe for the picking, while the Oracle of Omaha's top holding is sending all the wrong signals.

Warren Buffett is known for buying stocks when they're undervalued -- and then scoring a win after the rest of the market realizes the strengths of these particular players. This is the case with his investment in one of today's most well-known companies.

Such a precipitous increase in the value of U.S. equities has stirred up the usual cacophony of equity-bears screaming “bubble!” “Bubble” is a popular term, but, as it turns out, is rather ill-defined and fuzzy.