This one's the stuff of tragic cinematic lore. Brandon Lee (the son of Bruce Lee, who also died at a younage; he was 33) met an untimely demise during the filming of The Crow when a dummy bullet actually fired from a prop gun and hit him in the stomach. He was only 28 years old.
Apparently, someone in production had wanted the film to look more real, but didn't know that the bullet would end up dislodging and actually kill someone. What makes this whole situation pretty eerie is the fact that, apparently, Lee believed his family was cursed, because his grandfather had pissed off some Chinese businessmen back in the day.