Just had a shower thought (and I don't even know how I would go about searching this online), how many "one-off" fruits are there? I just rewatched a couple pre-skip episodes and forgot about the rust-rust fruit guy and how we never see him again, along with a brief mention by Zoro that "It should be no surprise there'd be devil fruit users among normal marines". Are there any other fruits that we see for a brief moment but never again?