Planetes is amazing if you love a good (realistic) sci-fi drama.
Sayonara Zetsubou Sensei is an excellent (darkish) comedy.
21st century boy is a classic saga. It's long, but kept set me at the very edge of my seat for its entire length.
Yotsubato is a cute slice of life manga about a little girl living together with his father. (also know due to the protagonist being the mascot of 4chan)
I will check out all of them, thanks!