Ecolab ( ECL), a producer of cleaning and sanitation products for the hospitality and health-care markets, gets Goldman's highest ranking of all 50 stocks, with a quality score of 94. It's expected to post earnings growth of 17% in 2012. S&P downgraded Ecolab two notches Monday, saying its acquisition of Nalco Holdings last week increased its debt leverage and that, along with a $1 billion share buyback program, is expected to raise the company's financial risk. S&P now rates Ecolab at triple-B-plus. Its outlook is stable. Ecolab's shares have a three-year average annual return of 16%, resulting in a market value of $12 billion.