Baccano! made me feel pretty damned good with it's awesomeness. Yeah, my butt totally hurt and my eyes and head felt weird from sitting there are and watching it all in one sitting, but I wouldn't have changed that experience for anything. That show was amazing and totally worth it. (Though, I don't think I'll be watching a series all at once again.)
Mawaru Penguindrum gave me that, everything-is-well-in-the-universe feel when I finished. You know what I mean, right? That totally content and peaceful feeling. I can't speak for the rest of the fanbase, but I was absolutely satisfied with how it ended. I loved it.
Red Garden is the only series that I've watched that made me want more IMMEDIATELY after I watched it. Sure, I've missed shows before, but there are few shows that I've actually watched from beginning to end more than once. And those few rewatches certainly didn't come right after the first. But for whatever reason, right after I finished Red Garden, I watched it all again. And again. And again. And again. I've never done that before. I guess it just really hits the right cord with me.