These investors have built a successful career around their ability to spot winners in the stock market.Bill Ackman of Pershing Square Capital Management and Andreas Halvorsen of Viking Global Investors are two billionaires worth following for investment ideas. They are entrusted with billions in assets to manage for clients, and that reflects a career of making smart investment choices. Alphabet (GOOG 1.17%) (GOOGL 1.12%) and Salesforce (CRM 6.14%) are two stocks these firms held in the second quarter. Bot ...