The latest 13F season is here, when many money managers issue required reports on their holdings. It can be worthwhile to pay attention, as you might get an investment idea or two by seeing what some major investors have been buying and selling.

For example, consider Citadel Advisors, founded and led by Kenneth Griffin. It's one of the biggest hedge fund companies around, with a reportable stock portfolio totaling $76.8 billion in value as of Dec. 31, 2013. According to the folks at Insider Monkey, Griffin and his team use "a combination of advanced computer code, complicated financial algorithms and secrecy. Griffin was using quantitative, technology-based methods before many other firms had cell phones."

Citadel Advisors' latest 13F report shows that it boosted its positions in Fifth Third Bancorp (FITB 0.20%), Coca-Cola (KO 1.30%), and Pfizer (PFE -0.17%).

Cincinnati-based Fifth Third Bancorp has been responding to customer preferences in part by experimenting with more self-service features in branches, such as advanced ATMs that do more than take or dispense money. Bank of America Merrill Lynch analyst Erika Najarian upgraded Fifth Third stock to buy last month, citing its valuation and seeing it as a defensive investment. The company's fourth quarter featured earnings per share up 22% from year-ago levels and record full-year net income. Fifth Third Bancorp stock yields 2.1%.

Coca-Cola stock underperformed the market in 2013, facing weak international growth and challenges from regulators and health advocates. Its last quarter was disappointing, with revenue and earnings lower than year-ago levels -- though market share in soda has been steadily growing in recent years. The company has outlined five strategic priorities, including accelerating sparkling-beverage growth, expanding its portfolio, and winning at the point of sale. Coca-Cola stock yields 3.2%.

Pfizer stock also yields 3.2%. As with other big pharmaceutical companies, its blockbuster drugs face patent expirations sooner or later. Pfizer's 2014 and 2015 revenue is expected to pull back because of expirations, therefore its pipeline of new offerings is paramount. Some treatments generating optimism target breast cancer and pneumonia. There's also hope that its drug Lyrica might be approved to treat restless legs syndrome. Pfizer's fourth quarter featured shrinking sales of Viagra and Lipitor due to patent expirations abroad and at home, respectively.