I've been using the silenced M4 with CCO for some time now, very happy with it. Ammo is readily available in military locations and thinning out the Z population with a silenced weapon while sneaking around is just great.
And for PvP IMO there's nothing better than a silenced, fully automatic weapon.
I've tried several sniper rifles (DMR, SVD) but they're far too situational to use for my tastes to justify carrying them around in the backpack.
"...late afternoon the Air Tasking Order came in [and] we found the A-10 part and we said, "We are going where!? We are doing what!?"
Capt. Todd Sheehy, Hog pilot, on receiving orders during Operation Desert Storm