Sayonara, Zetsubou-Sensei is an obscure manga/anime with my favorite openings and OP. The opening perfectly sets the tone of this weird series.
A high school girl walking to school in a beautiful cherry blossom filled day...only to see some one hanging on a noose on a tree. And she proceeds to more or less swing on his legs telling him he as so much to live for breaking and snapping the rope and pissing him off because she just almost killed him only his allowed to do that. The scene ends with A meeting that was never meant to happen.
Yeah its not a show or manga I recommend because its very very very weird and you have to go into it with that in mind. But not only was that scene well animated and beautiful in the show itself it pretty much sets the tone for the humor and character dynamic.