In my opinion: Assualt = SWAT 556 with the Auto Switch and Gernade Launcher attachment.
SMG = Peacekeeper with any attachment.
Pistol = KAP 40.
Launchers = SMAW (humans and equipment) = bad to the bone.
LMG = LSAT all round best stats
For Run & Gun (tactic)
Perks
1=Flak
2=Cold blooded
3=Engineer
Lethal =Syntax
Tatical = Concusion