Hi, Hari,
I'm new to the site, but back to PbP after a several year hiatus and I missed the quick creative process of 1x1 in particular. Some of your ideas that appeal to me are:
Childhood friends reunited
A work place scenario..possible adulterous undertones
Ex's reunited after a considerable amount of time
I prefer FxF, if you're up for it. Mature themes are welcome, so long as the story is the focus. HMU if you're interested.
~Lethe