I posted a similar thread in the Batman forums a while ago and we got some really cool ideas thrown around, so I thought I'd do the same here.
Title basically says it all. Forget origin stories. We have a billion of those. What we dont have a lot of are the "final days" type of stories; the ones where the hero has their last battle and their story ends. You know, tales like "Whatever Happened To....."
So if you were going to tell the definitive finale for your favorite DC character/s, what would that story be? No continuity restrictions; use, ignore, and/or change what you like; it's just you and the version of the character as you see it in your own mind, and his/her ultimate last story.