Always use the REV-46 with an unfolded stock using this build. It might not be the best but the strafe speed with this thing is on par with the pre-nerf Superi. Again, ammo is a huge problem with this gun as well and since it's bugged, you have to buy a loadout to get more ammo.
The Striker is the honorable mention because it's just so consistently good. Sniper support? It can do that. Mobility SMG? Not the best but the TTK is nuts. Main gun? It's an SMG but you can really use it like a close range AR. It is by far the most versatile gun in Warzone at the moment.