1965 Nobel Laureate in Physics. He was awarded the noble prize along with Sin-Itiro Tomonaga and Julian Schwinger for their independant development of Quantum Electrodynamics.
Interestingly enough, Feynman did not want to accept the Nobel Prize at first (he didn't want the "trouble" that it would bring) and only accepted because it would be more trouble to refuse.
He helped to figure out that faulty O-rings were the cause of the Challenger disaster.
His explanations of the fundamentals of physics found in The Feynman Lectures on Physics have help many a student and physicist since they were first published.
Worked on the Manhattan Project.
Developed Feynman diagrams, a visual way of calculating the rates for electromagnetic and weak force particle interactions.