Fate/Zero (although I wouldn't put Fate/Stay Night in that category aswell) is absolutely brilliant past the first episode of lore layout, especially if you like a bit of action in your gloom.
And YES, MONSTER. Thank you for reminding me of that, Chuckles.
Personally, I wouldn't really recommend Mirai Nikki though, as I feel it was rather uninteresting due to the shallowness (or in the MC's case, stupidity) of the characters; I feel that Yuno, the yandere the series is famous for, is victim to this aswell since it just looks like the creators made her kill lots of people and portray that as "crazy", which ultimately made her a bit shallow for me. The concept is simple and great, and there are some decent moments, don't get me wrong, but there's a lot of vague plot details and bullshit in what's going on that kinda threw me off the series.