This is one we did in a group awhile back, but it can be fun to do on your own, or with your own group. The way it works is that each person in the group pulls out an object from their pocket or purse, and then hands it to the person sitting next to them, to the right. Using the object passed to you, plus whatever you may know about the person who handed you the object, write for 15 minutes a fictional account of why this person is carrying the object. Work in a conflict, if you can. If you're doing the prompt on your own, either pull out a random object from your purse or from a pocket or purse from someone in your household.
When we did this in a group the first time, nearly everyone handed over a set of keys to the person sitting to their right. Then, nearly everyone wrote about driving. Nobody would admit if their fictional characters came close to the real characters, though.