America's Army: Special Forces/M24 Sniper Rifle
See also: M24 SWS
A bolt-action Advanced Marksmanship Rifle. Slow rate of fire, but maintains the scope when firing, and is relatively quiet. Clicking the 'fire' button when reloading will stop it for getting off a quick shot.
It has an internal 5-round magazine. Because it is bolt-action however, it takes quite a while to reload completely. Very accurate, unless you are standing or walking. But once you learn to fire this while standing and walking, you'll be a force to be reckoned with.
Also, practice without the bipod; you'll be better off without it.