Mine would be like the mansion quest for the Dark Brotherhood in Oblivion, except they're all out to kill eachother. But but but, that isn't the best part. They wouldn't want to kill eachother because of pay, they want to kill them because I've persuaded them to believe that the other mansion members are conspiring against you, kind of like who snaps first.
Starts with a house of 10. Last man standing is considered the "Alpha Dog" and given special priveledges. But they don't win their freedom, another 10 are thrown in with him, this round they'd be told that he is conspiring all their deaths and they must work together to defeat him with his special "Priveledges"(weaponry and such). However, I would inform them that there is a mole in their midst.
God, my ideas for each new round go on and on.