Michael Jackson. I was obsessed with him in the year leading up to his death. I was literally listening to his 2008 King of Pop compilation album when I loaded up MSN that morning and saw the banner saying he had passed away.
I am struggling to think of a single one that even changed my mood. Sounds like I am not as invested in people that I have never or will never meet or get to know as themselves as the rest of you are. Emotional investment I have no problems with, but "celebrities" can't mean much to me.
I've never really been hit-hard by any celebrity deaths at the time of them happening. With the exception of maybe Amy Winehouse, which still affects me to some extent, I wasn't a massive fan or anything, but just knowing she died at such a young age, from alcohol intoxication, it just scares me, and is one thing that's prompted me to make changes recently. I know so many people die from drugs and alcohol, it's just where I was at the time of her death plus her age.