Warren Buffett is an investing icon. His track record compounding capital for Berkshire Hathaway has made him a legend. The smartest retail investors closely follow his moves to find ideas for their own portfolios.In the conglomerate's $258 billion portfolio, the second-largest holding shouldn't be ignored. It's a position the Oracle of Omaha has held for decades, so it deserves a closer look from investors.Is this financial services enterprise the best Buffett stock to buy with$1,000 right now?A Buffett-a ...