If this was Manga, Berserk would be my #1 by a longshot.
As for anime, my top 10 is like:
1 - Hajime no Ippo
2 - Hunter x Hunter
3 - FMA Brotherhood
4 - Magi: The Kingdom of Magic
5 - Berserk
6 - One Punch Man
7 - No Game No Life
8 - Boku no Hero Academia
9 - Kaiji
10 - Naruto: Shippuden