One Piece Game
I've been thinking for nearly a decade about what system could work best to capture the tone and mechanics. I've hacked dozens of systems.
These days, I firmly believe OVA 2e would work the best out of the box. It has named fighting moves with room for variation and evolution, it has characters with quirks, flaws, and melodramatic tension. Since December, I had been meaning to try something with my local group before quarantine happened. We only managed a test session featuring a single PvP fight in a generic superhero academy setting.
That said, I'm uncertain how well I could run a game in any sense following Oda's storyline. The protagonists absorb so much plot and faction attention, original characters wouldn't have much left to play with. I think you'd have to ignore Luffy and set a game forward or backward in time with an original crew in another small-scale sea, somehow still inspired by the romance dawn of the death of the Pirate King.
While I've GM'd for a lot of systems, I've never run a shonen game, so I'm still trying to hone my skills to produce a story that feels appropriately epic/dramatic/feel-good like One Piece arcs tend to be.