Ak-47 with stopping power, deep impact and iron sites for me. The only other gun i might use is the mp5 with red dot or silencer.
BTW, if you use a m14 with the ACOG you can sprint like 8 extra steps, not that you'll be able to hit shit when you get to them
Another thing I like to do with semi auto guns like the m14/g3/deagle/and the semi-auto snipers is use the scroll wheel to shoot. Bind mwheelup +attack;bind mwheeldown +attack. Just flick the wheel back and forth for super fast shots. Some people think you're hacking haha