A Mosin-Nagant 91/30 configured for sniper use. Earlier models come with the PE scope, and later models the PU (the scope seen in Enemy at the Gates and Call of Duty).
Nowadays, these are hard to come by. Even if you do find one, they are about $400-$500+, which is 5-10 times more than a standard Mosin-Nagant.
Vasili Zaitsev's weapon of choice was the Mosin-Nagant sniper.
"Dad, if you buy me that Mosin-Nagant sniper, I'll be your best friend!
-Me, at gunshow
Basically a Mosin-Nagant equipped with a sniper scope. A favorite among the elite snipers, as it bring new meaning to the one shot kill*
*As it is a bolt action rifle (reloaded manually) it takes time to reload, ergo little time for a second shot. Meaning that the target must be taken down with one hit, or you're cover is blown. (while you normally would just fire twice)