Haibane Renmei

Haibane Renmei is definitely one of my favorite animes as well.
At first, I was drawn to it because it was quite thought provoking, a quality I look for in all the stories I watch/read. However, I quickly came to the realization that Haibane Renmei is an excellent, 'heart-warming,' tale as well: it has far more to it than thought provocation. I daresay that no other anime has captured human (or human-like) emotion and memory--or so to speak--so well.
Haibane Renmei also serves as an excellent example sheer humanity: that Glie, the walled city, almost seems perfect, even though it must face many of the issues that any other city would face, disregarding many "modern" issues.

Really, though, I could attempt to articulate the greatness of Haibane Renmei for far longer than most are willing to read: go watch it for yourself; you won't be disappointed.

Jam it back in, in the dark.