I play SND, that being noted I will describe my game tactics and what I feel is my favorite setup. I have A-40s, and while I may not be sound whore of the year being silent and hearing enemies in 7.1 is a huge bonus. I enjoyed rushing back in MW2 (lightweight, marathon, ninja) and in W@W I used extreme conditioning; Black Ops failed me since I would of had to of given up ninja =( , which wasn't going to happen. So it is a 97% that I will use Extreme Conditioning and Dead Silence, my tier 2 perk will either be Blast Shield (so I can focus on the enemy more than going around super careful "hmmm is there a claymore around that corner" compared to "I AM RAMBO rush around that corner!!!!!" lol. I have never been much of a camouflage/ghost player but Assassin does seem useful for motion sensors and heartbeat sensors WHICH WILL MOST LIKELY BE OVERUSED. If too many people with dead silence rock motion sensors or heartbeat sensors I will toss on Assassin, kids without dead silence will get shit on anyways, even if they camp. Take one step and I know exactly where you are bitch lol.
TLDR:
Extreme Conditioning
Blast Shield or maybe Assassin
Dead Silence