One Piece is my favorite...
Berserk is up there as well, but I think Ragnarok the Animation takes #2 because I like the Berserk Manga better (the ending was a shocker the first time I watched it... totally threw me off the series for months).
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"There. Cant lift your sword, huh? Tell me, what would it take for you to give up?" --Griffith
"You talk too much. Let me show you how to use your mouth on the battlefield!" --Gatts
My Anime List
Adopted FF character: Olan Durai