David Duffield

Payroll and human resources, twice. Duffield founded PeopleSoft in 1987 to run HR and payroll on client-server computers instead of mainframes, and it grew into a major enterprise software company before Oracle took it over in a hostile bid in 2005. He then co-founded Workday with Aneel Bhusri, rebuilding HR and finance software as a cloud service. Both companies won on a deeply unglamorous function every employer needs.