I know that many of you skip these, but even those who do should have their favourites..right?
Well, anyway. My favourite OP would be the Higurashi No Naku Koro Ni OP. Not only is it awesome and beautiful, but also does it role of introducing the viewer. to the mood perfectly.
As for the ending....these are usually worse then OPs, for the rule. However, there are some exceptions. I absolutely adore two first endings to code geass (season 1), Yuukyou Seishunka and Mozaiku Kakera