Any LMG with Target Finder and FMJ... there's a reason it's a default class.
It should be stock and suppressor as this would benefit LMG users more (Quickdraw Handle is a load of rubbish on LMGs). FMJ is a load of rubbish regardless and TF is overrated (it doesn't see through smoke unlike Dual Band). TF just needs some more visual recoil and the crosshairs not to go red when focusing in on a Cold Blooded user.
If LMGs were a 2HK at any range, suppressed or not, may be you'd have a point. Sure it feels kinda cheap being on the end of them but it means they are sacrificing a supressor or stock unless they use Primary Gunfighter, in which case they'd be sacrificing even more stuff from the pick 10 system.
According to our Facebook and Google+ community, the PDW-57 is the best gun. Or should I say the most often used gun.
You can see a nicely written article about the 10 best guns in Black Ops 2 here:
Only had the game 2 wks and the PDW is best SMG IMO though the MSMC is very close. I'm still experimenting with set ups, in previous COD I've usually used the ACR or SCAR as i'm not good at run around however MW3 run around was how to survive and reluctantly I've improved. As stated before it all depends on your style of play or the tactics needed for each game mode but overall the M27 with folding stock and grip backed by the brutal B23R pistol is what I'm running with at the moment successfully its not an aggresive set up but if you leave enough distance between you and the enemy you soon rake up the kills and get the scorestreaks away.