I suppose that would be Heath Ledger.  Marilyn Monroe and John Lennon both died before I was born.  Kurt Cobain died before my family left the cult, so I hadn't even heard of him or his death until years later.  I hadn't heard of Princess Di until she died. I've never known any of them personally, but Heath Ledger was an actor I'd seen in 10 Things I Hate About You, A Knight's Tale, and The Brothers Grimm, and I was excited to see him in The Dark Knight.

He seemed like one of those people it would be cool to hang out with, not because of some celebrity crush, but because I tend to think of celebrities as real people with real lives outside their celebrity status, and I wonder what they're like outside that life.  I was sad not just to learn of his death but to find out that he had problems severe enough that they lead to his death.  I typically want to believe the best of people and wish the best for them.  He was also only two years older than me, to the month.