Basically you play HORSE, and for the given actions, you pick a limited time to complete what you would like to do, and what you would like to do can be either certain parkour actions throughout the map, certain goal points, or certain kills, styles of kills, and any combinations you pick.
So, for example on my turn, I would pick a 20 second objective time, and during it, I would go to a high point on a map, and along the way, kill 3 guards, or maybe, do some sort of unique map objective action, like blowing up a door. If I complete it, everyone else gets a turn to do the same. If they cannot, give them a letter.
This is just off the top of my head, so any ideas would be great to talk about, and any flaming, well, lets just keep that to a minimum please, it hurts my feelings.
Actually, you could even have all the attempts run concurrently.