Activist investor Bill Ackman, who runs Pershing Square Holdings ( PSH -0.77% ), has a large stake in Lowe's ( LOW -1.51% ). Along with fellow activist investor D.E. Shaw, Ackman shook up company management last year when he installed ex- J.C. Penney CEO Marvin Ellison at the helm, with the goal of improving operating metrics against better-performing rival Home Depot.