Samuel Colt is most famous for inventing the revolver, a handgun with a revolving cylinder that contains the bullets. He patented his creation in 1836 in the United States, but it didn't become popular until the time of the Mexican-American War and the Civil War.
Colt founded Colt's Patent Fire Arms Manufacturing Company, which still does business as of 2014, and quickly became a millionaire. Although he is most famous for the revolver, his company also makes rifles, pistols and other types of handguns. His most famous revolver, the Colt .45, also known as the Peacemaker, became the most popular gun in the American West.