The party comes across a magic amulet. This amulet will give each user two wishes, but the wishes almost seem to have a mind of their own.
Missions for any campaign in any city of any realm. As long as crime exists, you will be able to use this submission.
What about a 'criminal' society with distinct laws - for stealing, the larger the value of something stolen, the less punishment the courageous thief recieves (but must return it of course). For this pirates(?) caught petty thieves deserve to be punished harshly. If you take, you better take a lot.