Ackman's best ideas still look attractive at today's prices.Bill Ackman likes to keep his hedge fund, Pershing Square Capital, invested in just a few high-conviction companies. Indeed, it's hard to generate market-beating returns if your investments are spread so thin your portfolio looks pretty similar to the overall stock market. But Ackman and his team hold stock in just 10 publicly traded companies.Ackman is willing to deploy billions of dollars at once to accumulate shares in his highest-conviction bet ...