In American football, gunner is a position played by members of the offense on special teams during kickoff and punt plays. There are typically two gunners on the field for these types of plays. Prior to the snap, the gunners line up closest to the sideline. Their primary job is to sprint down the field as fast as possible and tackle the kick returner or the punt returner before he can run very far back up field. For this reason, speed above all, and then tackling ability, are the primary attributes coaches look for in a gunner.
Gunners have special value on punt plays. According to the rules of American football, gunners are the only offensive players on punt who are able to start running downfield as soon as the ball is snapped (rather than after the ball has been kicked). This means they have a running head start on the rest of the offense. The gunners are also eligible receivers, so on a fake punt (or in rare cases where the defense simply forgets to cover one of the gunners), the holder or the punter might throw a pass to one of the gunners, in which case they play the role of a wide receiver.
Because of their great speed, gunners often serve as backups to speed positions on offense or defense, such as wide receiver or defensive back. The counterpart on defense to the gunner is the jammer, whose primary task, as the name "jammer" suggests, is to jam the gunner at the line and try to delay his progress down field.
Although "gunner" is by far the most common term, gunners are also known by a variety of other nicknames, including "flyer," "shooter," "headhunter," and "kamikaze."
Some famous gunners in NFL history include Steve Tasker of the Buffalo Bills, a diminutive player at just 5'9" who is widely considered the greatest gunner of all time; Bill Bates, a gunner for the Dallas Cowboys known for his daredevil plays; and Matthew Slater of the New England Patriots, who has made 7 Pro Bowl appearances as a gunner.