I'm coming out of the closit now and admitting that I really really dig something that is almost universally condemned by fandoms near and far. It's my dirty little secret, but no more. I'm getting it off my chest.
I like OOC characters.
Specifically I like it when an author explores what would happen if the basic canon backstory stayed the same, but ONE character was drastically different. How would it effect everyone else? How would they cope?
What would happen if Mustang were not distantly protective of Ed. How would Ed and Al's missions have gone if they didn't have his support from behind? What would happen if Al turned evil?
I find the whole idea of an AU based not on changing the EVENTS of canon, but rather the personalities of one of the characters, intriguing. Admittedly some things seem to be harder to change and have it turn out well -- When turning bad guys into good guys, for example, writers tend to turn them either treacley sweet or spinelessly emo -- neither of which is any fun to read. But I imagine it could be written. How would it be if one of the sins didn't approve of the way the others were treating humans and decided to switch sides?
It seems like such a fascinating thing to explore, and yet, it is OOC, and therefore a guilty pleasure.