This is what I'm using and they aren't too shabby. If anyone plans on sniping, try some of these out.
My go to class at the moment is the c4 rush. I'll switch to the ghost class if the enemy is spamming satcoms. I'll switch to the sit rep if I get killed by an IED or if the other team is camping alot. (most of the time). Lastly, I use the silencer and extended mags but I have the variable zoom on all these classes because I'm working toward the challenge for it. Oh yeah, and always have an armor piercing class set up just in case the other team is using ballistic vests. It will make them one shot kills. I opted for no secondary because I"ll pick up the first assault rifle I find and use that.
You should always put the silencer on. It doesn't effect the One Hit Kill box at all. So there is absolutely no disadvantage to using it. In previous games, the one hit kill was to the stomach,chest,head. With the silencer on, it was only chest,head. This game is different. I am not sure if it was an oversight of the developers or what (probably because IW doesn't pay attention to detail)
If you don't put it on, not only do you show up on the minimap but your shot is heard across the map and the muzzle flash gives away your position, big time. Use it, you'll be surprised how much better you will do when everyone doesn't swarm on you just for firing a shot.