Godchild by Kaori Yuki
If you like dark, gothic, and slightly crazy, then oh have I got a manga for you. Godchild is about a young earl named Cain who evil and bad events seem to follow like his shadow. The cast includes Cain's manservant, Cain's younger half sister, and his psychotic but brilliant half brother. Each "episode" in the manga focuses on a different character and their relationship with Cain.
Godchild isn't as sophisticated as say Black Butler, but it makes up for it in sheer fast-paced zaniness. The first part of Godchild has a killer White Rabbit killing girls in an Alice in Wonderland themed way and it never gets more normal than that. There is blood and violence, but it's never that graphic and the plot moves so fast that there isn't a lot of time focused on gore. Godchild makes a nice difference from very serious manga or something as silly as Sgt. Frog (silly in the best possible way mind you, I love Sgt. Frog).