Isaac Newton and Gottfried Wilhelm Leibniz
Isaac Newton and the German genius Leibniz were math pals for years, writing each other long letters about new theories and calculations. However, Newton had remained tight-lipped over his development of calculus, so imagine his surprise when Leibniz independently generated it and published his findings. The dispute over which man was responsible for this revolutionary discovery made bitter enemies of the pair, and they publicly quarreled until Leibniz's death. History has favored Newton, but any die-hard math geek will tell you that calculus had two parents, not one.