WORST
Assault: MSBS (unless you put it full auto, then it's better than half the list)
SMG: K7... I don't understand how anyone uses it, garbage damage at every range, I've gotten hitmarkers from point-blank on Hardcore, nuff said..lol
Sniper: VKS.. not just because everyone else puts it, because it really is a pretty awful sniper rife lol
Shotgun: Depending on the situation and gamemode.. either Bulldog or Tac12
LMG: Amelia.. I know a lot of people like it, easily the best statistically, but it moves so wonky that most people destroy their stats getting used to firing the thing and actually hitting their targets
Marksman: IA-2.. a go-to weapon, even for me, but its stats are a bold-faced lie in game - its accuracy is horrid even at the best of times, dead-center from across the map.. miss.. miss.. miss.. aim above target, hit.. even the SVU, with worse accuracy statistically, can dead-center from across a map without missing.. I think they got the stats flipped between those guns lol
Handgun: P226, the sites are off-center down about a quarter inch, meaning that stand-still headshot attempts hit the chest, its damage after close range virtually vanishes to the point it takes multiple hits even on Hardcore
BEST
Assault: ARX.. I find it to be the best overall at about anything you're attempting, though it doesn't excel at any one thing specifically. If you want damage from far, the Remington, if you want damage from close, Maverick, if you want something that works all the gray area between, ARX.
SMG: Vector, if you're not open to a suggestion and want to stay strictly on the SMG list - good rate of fire, good damage, use the right perks and you'll be dropping lines of enemies. If you are open, just put Stalker on and run the Honey Badger, since based on its size and base damage, it is clearly a SMG just on the Assault list lol
Sniper: USR.. it's mobile, recoil compensated, and smooth as silk once you get a rhythm.
Shotgun: FP6.. it might be pumpaction, but put a sight, a muzzlebreak, and slugs on it and you'll be sniping people with a damn shotgun in no time lol
LMG: LSAT.. like the ARX, not great, not bad, just the best all around from any gray area (which is most of any match).. a lot of mediocre weapons on a list can become amazing with the right perks and a bit of skill.
Marksman: SVU.. I know, it has the worst statistical accuracy, but as I stated above, it and the IA-2 have clearly gotten their stats swapped around. It hits spot on, where the IA-2 has a severe accuracy problem, and it kills in one to two rounds from the chest up, even though stats suggest the IA-2 should be doing that.. when it most certainly does not lol It seems every CoD has two weapon's stat lists swapped where one out-preforms its own numbers and charts in every way, and the other can barely keep pace with its own chart. This is this games example.
Handgun: MP Grach.. good stopping power, greater accuracy. The only reason it has ups on the Mag is its fire rate wins more one-on-one fire fights with the Mag.. lol