Outside of the the guns, almost all my classes are identical.
The AR's that I run with the most and do decent with are the XR-2, HVK, and Man-O-War.
On the XR-2 I usually run Red Dot, Quick Draw, and High Caliber. (I sometimes switch out High Caliber for the Suppressor.
On the HVK and Man-0-War I use Red Dot, Quick Draw, and Grip.
SMG wise I use the Vespar with Grip, Silencer, and Laser or the Razorback with Red dot, Grip, and Quickdraw.
I really do not use snipers, lmgs, or shotguns.
I use a launcher for every class except the Vespar.
I do not use any tac or lethal grenades.
All my perk setups are the same except for on the Vespar. My standard setup is Ghost, Hardwired, and then I use a wildcard to get both Dead Silence and Awareness. On the Vespar I run the same thing except I also add a second tier 2 perk in Fast Hands.
If I know I am going to be playing Domination, then I may have a class setup with Flak Jacket instead of Ghost.
I do not have a favorite specialist because I have only used a few just trying to complete all the challenges for the character. I've really only used the Prophet, Battery, and Outrider character's extensively. Probably my two favorite abilities are Glitch and the War Machine.
The HVK is the gun that I have the most kills with and is my go to gun if I am struggling. Since I have been playing a bit more Hardcore lately, the XR-2 is my second choice for it's range.