CEO and President, Sam's Club, Walmart, 54
Four years in as head of Walmart’s $57 billion warehouse club division, Brewer is upping the attack on Sam’s Club’s bigger rival, Costco. She’s looking for an edge through e-commerce, implementing in-store pickup for online orders and launching an app that lets customers pay without going through checkout. She’s also investing in food offerings (more organics), remodeling stores, and locating new ones in higher-income areas. There’s more to do; Sam’s Club’s revenue, operating income, and same-store sales were all down over the previous year.