Mania: Every season has its hits and its misses. However, most fans agree that there are certain elements that make an anime a "must see" title. Among these elements are the four fabulous fillers: The beach episode, the hot springs episode, the school festival episode, and the ghost story episode.
I remember that Cowboy Bebop episode, it was great :)
Now for the shows I don't know, I should go check them out...