The "Turtle Men"
Weapons---Akimbo Model 1887's and Riot shield (usually worn on the back)
Perks---------Marathon, Lightweight, Commando
Strategy----Nothing. They simply go around blasting people.
The88thPanzer's Solution: Long Range Weapons (Sniper Rifles), Accurate Launchers (Thumpers and AT4's), Hidden C4/Claymores placed in the most used route to your position.
Weapons---Various (mostly shotguns in my experience)
Strategy----Locate spawn points and kill players as soon as they respawn
The88thPanzer's Solution: Spawn "Guards" (have a teamate hang around NEAR spawn points to bail you out)
Strategy------Hide in isolated location and kill partner over and over until nuke is acquired.
The88thPanzer's Solution: Call in UAV's or Hijack UAV care packages and look for players that aren't moving much or a pair where one keeps reappearing by the other. Hunt down and kill in your own manner.
NOTE: These solutions are just my idea of how to deal with players that seem "noobish" to others. If you disagree with my methods, that is your problem. These are common situation that do not bother me since I follow the tips above.