226. Randal Kirk
$3.3 billion * self-made score: source: Pharmaceuticals age: 63 residence: lake Worth, fla. J.d., u. of virginia ’79 His biotechnology conglomerate Intrexon churns out such innovative products as nonbrowning apples and genetically modified mosquitoes that neutralize their disease-transmitting peers. Kirk worked while an undergrad at Radford University, selling cars and motorcycles at a nearby dealership.