John Bellingham
John Bellingham's claim to fame is that he remains the only person to have successfully carried out the murder of a British Prime Minister. His shooting of Spencer Perceval in 1812 stemmed from his long-held grudge against the government, which he blamed for not stepping in to help him when he was thrown in prison in Russia, where he was working. Upon his return, he asked for compensation and when that failed, a civil servant told him that he was free to try something else to get the money he felt he was owed. Taking this advice rather literally, Bellingham went to Parliament, waited in the lobby until Perceval appeared and shot the Prime Minister through the heart.
Bellingham was tried two days later at the Old Bailey, where he remarked that, while he would have rather killed the British ambassador to Russia, "I trust that this serious lesson will operate as a warning to all future ministers." He was found guilty and sentenced to death by hanging.