Anime series' you want more of

When you find an anime you love, there's one thing you'll always want...and that's more of that anime!  Very rarely do we see an anime series where everything is wrapped up and answered by the final episode.  If you're really lucky, that 'final' episode leads into a movie or two that explain more things, but only leave more questions in the end.  As the saying goes, you always have to leave your audience wanting more.

Looking for more from a specific anime series shows that the series' creators did a fantastic job at building a believable and interesting world.  If you didn't want more content, they've simply failed to do their job.  It's definitely better to end before your time than to wear out your welcome.  Indeed there are some anime features that have been around so long that it's nearly impossible to keep up the original quality.

With all that said, I'm sure we can't help ourselves from being just a tad selfish.  Even if there's a fantastic anime series out there that ended on a high note in top form, we can't resist the urge to call for more.  Just one more storyline where we find out what happens to the main characters.  Just one more conversation between cast members.  Just one more chance to get that 'new' feeling once again.

If I were being selfish, I would absolutely love to see another season of Birdy the Mighty.  That was an anime series that only got better with each episode.  By the end of the second season, I was blown away by how far the series had come.  Characters had really been built up, some impressive animation was shown and there were all sorts of storyline avenues to be explored.  Unfortunately, it doesn't seem like a season 3 is in the works.  I'm not quite sure why that third season isn't happening, and it kills me to know that some of my questions will never be answered.

If you could pick one anime series to return, which one would it be?  What anime would you like to see given a second chance?