Using the US rating system is common in other fandoms
Sorry, just wanted to point out that this is no longer an option. The MPAA threw a fit last year, and threw suits at a few fanfic sites. So a lot of sites went through and had to redo their ratings systems. It sucks, but there it is.
I believe Yvonne's Clark Kent, This Is Your Life had an nfic version that had more to do with the situation and violence than anything sexual. I think there's a few others, but that would take some searching... and I wish I had time to read right now!
Just edited to fix a typo in the quotes code which was preventing it from working. - LabRat