Gone Girl - 8/10. I've never read the book, so I wasn't privy to the ending or the twists throughout. The structure of the book of two narratives is done really well, though. It's a cynical social satire that meets murder mystery. It's quite like The Game in parts - but it's also got ties to The Social Network in terms of the humorous undertones/emphasis on social media, perception etc. It's a masterfully made thing and Fincher again makes an amazing piece of cinema - Affleck is OK, I wouldn't say any better than that, but Rosamund Pike is really powerful as Amy. The soundtrack - by Trent Reznor and Atticus Ross, like The Social Network's - is really powerful and atmospheric, too.
I genuinely can't think of a bad Fincher movie. People talk about Nolan, Tarantino...he's up there with them for me.