There's a reason why Robin Williams was the go-to-guy to play a genie, a professor, and a therapist: the man exuded an air of wisdom unmatched by any of his Hollywood contemporaries. Simply put, Williams had a certain gravitas that was undeniable. Whenever he stepped onto stage and came onto a scene, he commanded every moment. His energy and his prophetic voice were impossible to ignore, making him the perfect man to take on the most influential roles and deliver the most inspirational speeches. From his scenes in Dead Poets Society to snippets from his stand-up, these are Robin Williams' most significant monologues.