I think it was Writer's Digest that had a calendar in each issue where each day had a brief (one or two sentence) writing prompt. In digging around on the Interwebs for some info that I couldn't find in my rule and source books, I found this little gem:
http://surbrook.devermore.net/herosource/champions/crime.htmlI'm not in any way suggesting that you or anyone needs it, but it looks like something fun to try once or twice, be it for a writing project or an evening's gaming.