Ganked from eustacia_vye:
Inspired by Doctor Who's "Turn Left": Pick one of my stories and tell me a point in the tale that you'd change, something tiny (e.g. "and then Fay chose silver glitter instead of gold") or big (e.g. "and then Rose was arrested instead of Jack"). I'll tell you how that one difference would have altered the course of the entire story.
Fics are in various fandoms according to tags, but all except for the most recent can be found on SilverFic.