I guess most have, humans are violent after all, but for me it never reached such resolution that I would ever go through with it. I mean, I've thought that the world would be better of without some people, though it was a long time ago, it still happened.
Nowadays I ponder other things and don't have time with such dull thinking/wishing.
EDIT: Also, please refrain from making threads with such extremely sensitive topics btw. I'm not saying that it is wrong to talk about it or so, but on a forum the conversation on such topics seldom remains moderate in nature. Besides, most wouldn't dare answer, because good boys and girls says it's wrong to kill or even want to kill, keeping up the social facade, which is vital at most times for our society to function, regardless of how mad it is. I'm not implying that I think it is good to kill, so don't get me wrong, I think it might be the height of stupidity.