My weekly roleplaying group has been using rules based on the Over the Edge system for our latest game. One of the rules I really like involves character creation: each character needs a secret--a secret that should come back to haunt them as the game plays out.
How is this working out gamewise? Not all our secrets have come to light and, of those that have, not all were earth shattering. But the revealing of one character's secret had an intense impact on the game while the secret of another character turned out to be a clever red herring in the overall plot.
Of course, the writer of a story, as opposed to the dungeon master of a game, has much more control over how integral to the plot the characters' secrets turn out to be. So I think I'm going to add 'secret' to my character sheet. Some characters will have big secrets, some will have small secrets--but a secret of some sort should add some spice to each of them and will open up new plot possibilities for me.