You just reduced my work load, my vote also goes to Truth of the Elie Arc.From Haru's emotional trial for the Rave of Truth to the revelation about the true nature of the world, from the journey back to Symphonia to the true story behind Elie and one of my fav twists i have read in manga overall. The Truth of Elie Arc had it all and is my personal fav, so the vote goes there.
Sad to see that Tower of Heaven didnt get in, but happy that Phantom Lord made it since the arc needs the recognition it deserves.
Mashima is at its best there.