Lady stoneheart visits Walder Frey - concept art

Lady Stoneheart

This scene has been in my mind for a very long time. I still remember those many times I had to read AFFC final chapter, because it was truly unbelievable. I think the shock was not only because of the Lady Stoneheart presentation itself, but also for the big immediately question after that: how much will it take till she "visits" lord Walder?
Of course, this is not canon and possibly there are many other lectors who don't agree with this possibility. Even I've heard many times that opinion about the not-revenge-lesson lying beneath Martin's work. Putting all these judge/karma-interpretor roles apart, I think there's just one thing clear: you don't finish a book with this kind of chapter in case you don't want people to do one thing: to imagine.
And this is what this scene is about.