Italian surgeon who laid the foundations of the mathematics of probability in 1524 and "discovered" complex numbers in 1540 (HardCorePlatonists of the world unite). Not as well known as he might be, given the importance of both to the foundations of our understanding of the universe in QuantumTheory.
See Gerolamo Cardano - when we get around to it for more about the trials and the paranoia of this amazing Renaissance gent.