Well that is hard because nothing is really like Death Note. I mean, you can read the manga and be disappointed at the face it shots its load way too early.
What about the story did you like so much that want to see more of? Was it the drama, the suspense, the pragmatic hero, the whole good intentions may lead to disaster, the tone, etc.
All we got is "I don't want to see mechs"
Monster: Should be similar in tone and suspense. I personally thing the series is too long and I didn't like it....but I will not say why because it most like will not bother you.
Darker than Black: The lead character is also very pragmatic. He will do whatever is needed to achieve his goal. That includes anything from torcher, murder, being a traitor, etc.
Kino's Journey: The only thing they have in common are the morally ambiguous questions that don't really have a right or wrong answer. It is thought provoking, well animated, very well dubbed, and honestly the only anime I have mention that I honest think is good. I don't know your taste, but if you want to see something intelligent that will keep you thinking, this is for you.
