Sometimes the mode you play can also impact what perk setup you use. For instance, making use of Flak Jacket in Domination is highly useful with how often Frags, semtex, and C4 rains down on you while trying to cap. a point. Then you have other things which are situational such as a stealth (Ghost) class with a suppressed weapon to compliment, for those matches where the enemy team is heavily relying on their UAV. The PDW is a good SMG to make use of this type of setup.
Another is the Engineer class. If you're someone who finds they prefer care packages, having this on standby is great for when you're ready to call it in if you were using a class prior to it. Just swap classes upon death to make use of the re-roll then go back. An added benefit too, is you can throw EMP grenades on this class as well as (or even the Black Hat) Scavenger for your Perk 2 along with Hardline as your Perk 1. It can double as an Anti enemy equipment class when necessary and supply a bit more points quicker, should the enemy be more annoying than usual with such things.
Lastly, other things you may find useful are building classes like Cold Blooded to combat those rocking with their Target Finder. An Anti-Air class with the FHJ launcher for those instances the enemy might get lucky. Or even your own shotgun class for the times when hijacked becomes nothing but a shotgun spree. As they say, if you can't beat them, join them.... and show them who is boss while you're at it~
Remember, you can have multiple classes to handle multiple types of situations that are occurring. Don't design a class thinking it's the be-all end-all of classes. Pick a gun you feel does especially well for you and design around it with something specific in mind, and play to its better attributes if possible. EVERYTHING is capable of killing in this game.
Uploading gaming videos as a hobby, enjoy at your leisure~ http://www.youtube.com/user/BamboozledByAnime
Hipfire the s*** out of anyone within medium range, ignore/avoid anyone outside of it. Throw C4 into rooms before walking into them detonate it by double tapping X. Whenever you see red equipment throw an EMP at it. Your scorestreaks will work in such a way that if you earn one you should earn the rest. Try upping your sensitivity to atleast 6. Always sprint full speed round corners to ensure a brief second of invisibility to whoever is round there.