You rather use Assault-Automatic weapons or Sniper-Bolt like guns? My favorite classes are:
Primary: UMP.45 with FMJ (or Silencer if you want high killstreaks-stealth)
Secondary: Stinger to get that little chopper that prevents your team from winning
Lethal: Claymores
Grenade: Stuns, faster to throw
Perks:
Sleight of Hand (or Scavenger for high killstreaks)
Stopping Power (or Cold-Blooded for stealthiness)
Ninja
and
Primary: Intervention w/ FMJ
Secondary: Raffica Akimbo or Deagle FMJ
Lethal: Throwing Knife
Grenade: Stuns
Perks:
Sleight of Hand
Stopping Power
Commando
About killstreaks, I usually go UAV-CUAV-Emergency for map awareness or the Harrier-Chopper-Nuke for Atomic Blast