Baccano is probably the best anime I have ever seen.
When I first saw the genre description and the word "immortals" I was very skeptical. After all there are too much unsophisticated and frankly silly anime series with vampires. But how wrong I was!
The predictability of the plot is approaching zero, the story is dynamic and interesting. Despite the gore and blood the characters remain strangely good-natured, though sometimes in their unorthodox and unique way.
Overall, while watching Baccano you must always pay attention and think, you try and figure out what is going to happen next and you fail at it, but the feeling is fantastic.