Examples of games where players gravitate towards the dark side:
GTA

In GTA:SA, my current challenge is:

* Use passive resistance unless cornered. I.e., flee from a crime scene, run from police, run when a hostile gang takes a potshot at your car. Walk on the other side of the street when you spot other gang members, etc.

* ALWAYS proudly proclaim affiliation to Grove St. whenever asked by another gang (i.e., never tap Left in order to deny gang affiliation). Run like a little coward once they draw their pieces. ;-)

* Never kill any non-hostile target -- that is, the target must be aware of you and chasing you for it to be a legal kill. For purposes of completing the game's missions that require you to kill innocents (or when defending yourself from people who insult you) using hand-to-hand combat is considered non-lethal.

* Never kill cops, except when mission critical.

* Obey traffic laws. =) This obligation is waived on time-critical or chase missions, or when under duress (e.g., being shot at by rival gangbangers).

* Play the game as a severely obese character; never use the Sprint button.

* Never become "Wasted!" or "Busted!"

* Saving should be done only when quitting for the day.

If I transgress this, it's game over -- the save is deleted or overwritten with a new game. Or, as Ryder puts it, "That's game null and void, *****."

I've failed three times already, and I'm up to the midway point in the pre-San-Fierro story arc on my latest save. I haven't played in a while, but when I get back into it, I'll tell you when I fail. ;-)