I really like Knights of Sidonia and Psychopass too.

Other than those, I guess this would be my list. 

Black Lagoon
Claymore
Ergo Proxy
Ghost in the Shell
Welcome to the N.H.K.
Usagi Drop
NANA
The Twelve Kingdoms
Steins;Gate
Legend of the Galactic Heroes

I love all of these in some way or another, but if I had to pick a favourite I'd probably go with Legend of the Galactic Heroes. Usually long animes tend to be utter crap, but Legend of the Galactic Heroes was brilliant. It felt more like HBO when they're at their best than a long anime. It's easily the best space opera I've ever watched.