Given your list of favorites you seem to have a liking for the darker anime. Ergo Proxy btw is one of my favorites.
I would say try:
High School of the Dead.
Demon City Shinjuku
Angel Beats (funnier but a little dark too)
Higurashi no Naku Koro Ni
Requiem for the Phantom
Toaru Majutsu no Index
with the exception of Angel Beats most of these are pretty dark, some especially so like Higurashi. If you're interest in something a little lighter let me know and I can suggest some there as well.