I haven't done an anime ramble in a while, so here's a short one.
If you like dark stories, then you have to check out Attack on Titan. It's horrifying, creepy, often bleak, but there's still a thread of hope and perseverance among the characters that you can't help but cheer on. I warn you, though, it's not for the faint of heart. Some scenes are pretty gruesome.
The story: The last of humanity has sat behind its walls for 100 years, content in its illusion that their greatest threat, the giant, humanoid beings known as Titans, cannot reach them. But one day, an abnormal Titan breaks through their walls, and now they know:
Humans are cattle. Their home, a pen.
The main character is a young man by the name of Eren Yeager who swears vengeance on the Titans after one brutally murders and eats his mother. And he's the one man who might just turn the tide for humanity.
I've watched around 18 episodes, and I can't get enough. The Titans are a mystery that slowly evolves as the story goes on, and the Scout Regiment is badass. I fear for the characters' lives because it's sort of like Game of Thrones--you're not sure anyone is guaranteed to live.
Root for humanity. Watch Attack on Titan.