There is a local gaming group that meets monthly and I've been thinking about starting a semi-campaign of simple 3.5 D&D (no extra rules as I want everyone to be on the same page right away). I can't count on having the same players every time. You also can't expect people to remember much after a month, so I want each night's action to be largely standalone, one shot adventures, but I want people to be able to reuse their characters.
Here's the setup I plan on using.
You have been found guilty of a moderate level crime. It might have killed someone in an illegal duel, caught carrying illegal weapons, tax evasion, theft, import/export without the proper forms and fees, something worse than loitering and less than murder.
You may or may not have actually been guilty. Perhaps you are a foreigner ignorant of local laws or someone who did the honorable but illegal thing. That is now irrelevant. You have already been sentenced. The city of Neess is quite progressive and doesn't use execution or even maiming in most cases. The city loves to use fines. But if the person is too poor or the crime is too serious the person is Marked. Marking puts a permanent imageof a horned skull on a person's face. It magically shows through makeup and hoods. Nothing short of wish level magic can remove it.
Soon after your sentencing, you are approached by a mysterious woman. She informs you that she is from the Neessan council and would like to hire you for a secret mission. You will be paid. She has a secret spell that will remove the Mark for a week. The missions are quite dangerous. But, if you succeed in three missions, your Mark will be permanently removed and your name stricken from the crime record. She warns you that she has no official title and only a few people know of her existence - if they get caught, no one will believe that they are working for the government.
Your character is someone who has agreed to this proposal. Maybe the Mark prevents them from pursuing their earlier life and work. Or may they just want the chance to do cool dangerous stuff.
The adventures will be spy stuff in an urban fantasy setting: assassinations, object retrieval, finding out secrets, etc.