The Collaborative International Dictionary of English v.0.48:

Sharpshooter \Sharp"shoot`er\, n.
   One skilled in shooting at an object with exactness; a good
   marksman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sharpshooter
    n 1: an athlete noted for accurate aim
    2: someone skilled in shooting [syn: marksman, sharpshooter,
       crack shot]
    3: a fast schooner once used by New England fisherman for
       illegal fishing in Canadian waters

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "sharpshooter":
   Nimrod, Zouave, archer, artilleryman, bersagliere, bowman,
   cannoneer, carabineer, chasseur, crack shot, dead shot, deadeye,
   dogface, doughfoot, expert rifleman, foot soldier, footslogger,
   fusileer, good shot, grenadier, grunt, gun, gunman, gunner, hunter,
   infantryman, light infantryman, marksman, markswoman, musketeer,
   paddlefoot, rifle, rifleman, shooter, shot, sniper, targetshooter,
   toxophilite, trapshooter