2. Apocalypto
Here's an ending that comes out of nowhere but actually works, because it's rooted in some form of historical accuracy, and everything we've seen before is so savagely brutal that a little levity isn't such a bad thing. Jaguar Paw spends the majority of the film trying to outrun his pursuers and rescue his pregnant wife, during which we see countless decapitations and violent murders. Though it's reasonable to expect that Jaguar Paw will rescue his wife at the end, it's fair to say that it's not going to be smiles and rainbows. Still, the ending proves curiously upbeat in a much broader way; Jaguar Paw, who is absurdly outnumbered by this point, makes it to the beach to see boats full of Spanish Conquistadors arriving, essentially saving his family's hide and changing the course of the region forever more. How did he survive? Because...history.