Investors should always be taking a look at the investments of Warren Buffett and his company, Berkshire Hathaway.Warren Buffett, the 94-year-old chief executive officer of Berkshire Hathaway (BRK.A -0.03%) (BRK.B -0.07%), has helped the giant conglomerate build an equities portfolio that is now worth north of $315 billion. In this portfolio are 45 stocks. Of this group, Berkshire's top three positions are Apple, American Express, and Bank of America, which are collectively valued at roughly$168 billion as ...