This campaign was an experiment — and it ended up being a fun one anyway. Set in a modern super-hero setting, each of the players rolled a d10 to select a pre-generated character.
These characters were being transported inside tubes traveling across a military reservation in the New Mexico desert. Waking with complete amnesia, none of them had any memory or recollection of what their powers where. From there, they had to keep experimenting to learn who they were and what happened to the world.
At the first session, each player received a blank character sheet with only a physical description. Over the course of the campaign, they were able to fill it out as they learned more about their abilities and their past.
As part of the experiment, each subject had a number assigned (and tattooed on their wrist). Whenever that player rolled that number when attempting an action, they received a minor flashback from their history.
The Ten ended up taking a bit longer than I originally imagined, largely because it was a fun exercise, but it was a campaign with a specific beginning and ending to it.