1.) John Smith (c. January 1580 – 21 June 1631), Admiral of New England, was an English soldier, explorer, and author. He was knighted for his services to Sigismund Bathory, Prince of Transylvania, and his friend Mózes Székely. He was considered to have played an important part in the establishment of Jamestown, the first permanent English settlement in North America. He was a leader of the Virginia Colony (based at Jamestown) between September 1608 and August 1609, and led an exploration along the rivers of Virginia and the Chesapeake Bay. He was the first English explorer to map the Chesapeake Bay area and New England.John Smith (explorer) in Wikipedia
2.) John Smith, from Baltimore, was a Captain in the Baltimore Regiment during the American Revolutionary War. He commanded a company of 45 Irish Marylanders. He was captured by the British and condemned to death by Lord Francis Rawdon after several witnesses claimed that Smith had killed Colonel Stuart of the King's Guard when the latter was on his knees begging for mercy. Nathaneal Greene learned of Smith's plight from a British deserter. He sent a letter to Rawden under a flag of truce defending Smith, who was pardoned and paroled by Rawden.
3.) Sir John Smith (22 February 1754 – 2 July 1837) was a British army general. In his early career as a Royal Artillery officer he fought in the American War of Independence, and was twice captured and imprisoned by the Americans. In his later career he was involved in expanding the British Empire in the West Indies, helped keep control of the island of Gibraltar and commanded various artillery battalions.John Smith (British Army officer, born 1754) in Wikipedia
4.) In the book Mr. and Mrs. Smith
, by Cathy East Dubowski and the movie by the same name, John Smith is the pseudonym of a hired assassin. Unbeknownst to him, his wife, Jane, is a hired assassin working for a rival organization. Neither knows that their spouse is also an assassin.