Other forms: sharpshooters
If you know someone who is a crack shot with her rifle at target practice, you can call her a sharpshooter.
Annie Oakley, the fabled markswoman of the Wild West, is a perfect example of a sharpshooter. The sharp bit is a bit of a stretch, but it is presumed to refer to the marksperson's eye; sharpshooter comes to us as a direct translation of the German Scharfschütz. Today the terms sharpshooter, marksman, and sniper tend to be used interchangeably.