A thing I came up with and I really enjoy. Basically, in the future, some woman are created to do nothing but fuck. Mikasa is one of the best of these whores. This would be a sorta straight smut story, and possibly sci fi if wanted. She also could be done in by multiple characters at one, so keep that option open. This is one of my favorites to do.
This picture inspired me: (NSFW)http://markhenry500.files.wordpress.com/2013/06/mikasa-ackerman-3.jpg?w=707