There's already a general CoD thread. It's so this section isn't filled with many specific things about Call of Duty. "Favorite primary weapon", "best grenade", etc.
In the end, there's not much you can do about campers besides kill them in cheap ways, as in cooking a frag, C4 arounda corner and detonating instantly, Predator Missile, or even flashbanging them a few times and then cooking a frag. Personally, the "frag" option takes care of just about everything.
In FPS games I just hate walking around and all most people do is sit in buildings and other spots. It defeats the point of the game. The kill streaks give them incentive to do this, too. How else do they expect to get five+ kills? They sure as hell aren't good enough at the game to run around and get five+ kills, so they sit in corners waiting for people then spraying them. There are times when it's okay to camp, but otherwise it's just a waste of time and makes the game boring for most people.
In the end it's basically the same game since Call of Duty 4, I wish they would be creative and change the game some.
They actually did change it. They added more kill streaks, some new perks, attachments, weapon progression, a few overpowered guns (e.g. the machine pistol/FMG9, it's stronger than most guns, especially dual wielding them and having a few perks that make them better to use. And the PP90M1 makes all other guns irrelevant, it's a sub machine gun that is very powerful, has a large magazine, is fast, and has great mobility), some glitches that give you the ability to have no recoil and to stick your head out of certain places and people won't be able to kill you. So yeah.