Need a new anime!

[6ari8]

1) Hellsing Ultimate
2) Baccano!
3) Durarara!!
4) Fate/Zero

These are worth watching too
1) Higurashi no Naku Koro ni
2) Bakemonogatari
3) NHK ni Youkoso!
4) Gintama
5) Mirai Nikki

 

[Shusai]

Most have been mentioned.

Although not the type of anime you're looking for, Bakuman is a very interesting anime (with 3 seasons). It was made by the same authors of death note.

I just don't understand why its not that popular. (Maybe, the plot)