Edit: I agree with the post above me, but anyway, here are my best classes.
I've aready posted my main class setup in a lot of other threads, so I am actually going to show here one of my back-up classes.
SMG 1 (Named this one SMG P90TR, reference tothe good ol' P90 from COD4)
PDW57 Fast mags/Laser sight
Pretty good rushing class. I use it when I get bored of the next class. P90 PDW57 i useful for Medium range combat, KAP40 is useful in close range encounters. It i like they are made to be used togheter
SMG 2 (I named this class Yuyuko, and the weapon will have has cherry blossom camo on it. (Get it? No? AWWWWW... )
MSMC Laser Sight
Lightweight/Hardline or Flack Jacket (PERK 1 GREED)
Scavenger OR cold blooded
Ext. Conditioning/Dexetrity (PERK 3 GREED)
UAV/CUAV (or Hunter Killer Drone)/Orb. VSAT
VERY good domination setup. You are imune to explosives, and can get to objectives quickly. Laser Sight helps since you don't have the luxury of aim while capping Domination points, and the concussion helps slowing down your opponnents.
Assault 2 (AR alternate)
TYPE25 Laser Sight/Stock/Silencer (PRIMARY GUNFIGHTER)
NO EQUIPMENT WHATSOEVER
Basically an SMG mentality with an Assault Rifle build. You may prefer the FAST MAGS instead of the silencer, but If you master Reload cancel like I do, there is no need for that, and I like the irons, so NO to Optics.
Here is my default SMG class. I use this setup on all of my SMGs.
Primary Weapon: Any SMG
Perk 1: Lightweight
Perk 2: Scavenger and Toughness
Perk 3: Dexterity and Engineer
Attachments: Fast Mags and Stock
You will need to dance around when you get into sticky CQB or dropshot. Stock helps a lot in this area.
My class for Plaza/Hijacked:
Perk 1: Ghost
Perk 1 Greed: Blind Eye
No Perk 2 Until I unlock Scavenger again
Perk 3: Tactical Mask
Perk 3 Greed: Dexterity
Lethal: Combat Axe
Tactical: EMP grenade
Gun: Tac .45
Attachment: Long barrel
It's a fun set up and really tests your aim.
My Run and Gun class:
Weapon: Submachine Gun (any works, but I favor the Vector or MSMC)
Attachment(s): Red Dot, Laser Sight
Perk(s): Perk 1: Blind Eye, Lightweight. Perk 2: Toughness. Perk 3: Extreme COndtioning, Dead Silence.
Scorestreaks: UAV, (counter UAV or Care Package), Lightning Strike
Wildcards: Perk 1 Greed, Perk 3 Greed
This class I use for HC TDM, TDM, and Kill Confirmed, generally anything game mode that doesnt require me to be trying to catch grenades.
I have a few more set up but this is my main class. My domination classes are pretty awesome too if I must say so myself. Which I am sure I am.
primary: MP7. attachments: rapid fire, FMJ, fast mag. wildcards: primary gunfighter, perk 1 greed.
perk1: hardline, ghost. perk2: scavenger. perk3: dexterity
no one seems to use or like the MP7 anymore but i think its quite good (though not as good as MW3) also the gun emblem is in a good place...for once