Originally Posted by Yoda beer
Up Close And Personal - 10
You should also include that throwing a weapon will disable the achievement. So don't press Y+B and throw something like a baseball bat or a frying pan, whatever.
I never once pressed B but didn't unlock the achievement. I would assume it was because of the above reson. I was using grenades aswell, so that might be a problem to.
I will have to check it. I threw a grenade when I was playing and still got it. But you might be right about thrown weapons.