By far the saddest arc in One Piece. It completely broke me the first time I saw it. Up until this point, no one had ever died in One Piece, not even bad guys. To lose Ace, and see Luffy so broken.
ONE PIECE Sabo and Ace, wish Ace could meet Sabo a last time just to say "I am happy you're alive. I will give you my willpower, because our sake cups please take care Luffy until its dream finish"