1. Esther Boserup: A female economist from the 1970s, she revised Malthus and her book argued that population pressures stimulated technological progress in agriculture. She was a precursor of Julian Simon and also a pioneer of work on economics and gender.
2. Frederik Zeuthen: A mathematician and early game theorist from the early 20th century. He developed the idea of a bargaining zone, how to incorporate "free" commodities into general equilibrium theory, and refined the theory of monopolistic competition.
Jesper Jespersen is a reasonably well-known post-Keynesian. More recently there is Bjorn Lomborg, who am I forgetting?