DC CHALLENGE. DC, 12 issue series by Various.
The idea for this came up at a comics convention party. Each chapter is written by a different author, and drawn by a different artist. The author had to have the story end on a cliffhanger (which he had to have a solution for), provide the title for it, then turn it over to another writer without telling him the solution. Any DC character from their 50 year history was fair game to use.
Six authors did the final issue.