In my opinion, this is the best class to use:

Primary Weapon: M16A4 Attachment:Acog Scope
Side Weapon: M1911 Pistol (or Desert Eagle, which ever one you have or prefer) No Attachment
Special Grende: Stun
Perk 1: Bandolier, Claymore, 3xFrag or 3xSpecial Grenade
Perk 2: UAV Jammer, Overkill or Sleight Of Hand
Perk 3: Martydom, Last Stand, Extreme Conditioning or Deeper Penetration

If you have any questions or want a battle sometime add me. PSN Name: MikeyJoe1404 (no spaces) Good Luck :)