T. Boone Pickens Jr., an oilman and pioneer in hostile takeovers, has died. As the longtime chief executive of (PXD) an independent oil and natural-gas company he founded, Pickens’ folksiness, advocacy for shareholder rights, and populist vilification of “Big Oil” helped turn him into one of the most recognizable executives in the U.S. for decades. Two years later, he struck out on his own, forming what was later renamed Mesa.