I love going through a round with nothing but a scilenced pistol. Sneaking around and stuff. Popping foo's in the back o'their skulls. Knifing a terrorist trying to plant the bomb. Other such awesomeness.
Its even better when you have team mates who arn't Ramboing everything and actually like check corners and clear rooms and provide cover fire and such. I've only dealt with competent people like that about 4 times though but when it happens its really fun.