I've got to agree with the Sharqi strategy. I just got done playing a round and landed myself my first three knife kills. Well, it was technically my 2nd, 3rd, and 4th but my first one never found its way to my stats. I dunno but that's another story.
I've been playing for a while but never take my knife out. I'm not good enough to get the close. But I want that badge so I've got to start practicing.
Found a sniper who never had a clue until I crawled in front of him. Pop. Gave me all the time in the world to line him up too. Later, saw a guy trying to use a corner as cover. swish,swish,swish,Pop. Saw his buddy a few steps away. Pop. Two in a row. I nailed three in a couple minutes on a server running 10 a side. Without trying. but damn does my aim suck.
I was worried about that badge but I just need to bide my time and take the opportunities when it's back is turned. For all those who are worried, don't be. Just play it out and it will come. If I can do it, anyone can!