Is ONE PIECE episode 602 filler?
Canon No, episode 602 of ONE PIECE is canon.
#602
The Deadliest Weapon of Mass Destruction in History! Shinokuni!
史上最悪の殺戮兵器！シノクニ
Aired 30 Jun 2013
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.