While I'm asleep, just randomly one night without warning. Completely unexpected, like, not when I'm old and going to die anyway. As in it could happen tonight, if it wanted to.
Either that, or in a giant earth shattering devastating disaster. Some atomic explosion or giant meteor, and I'm really close to the impact point. That way, I don't live long enough to feel any pain or after effects, but I still get a nice fireworks display for half a second. That would be fun.