Controversial Least essential strawhat?

[Logiko]

If we are talking roles, most are essential:

• Captain
• Combatant
• Navigator
• Cook
• Doctor
• Shipwright
• Helmsman

Marksman isn't strictly necessary for the survival of the crew, specially when 99% of battles don't play out on sea.
Musician is really a bonus role, it only serves the porpuse of increasing the quality of the mood during the day.
Historian per se is not that useful for a crew's survival, but in One Piece it's focal because of the Poneglyphs.

If we are considering the whole character + his role in the crew, then Usopp is definitely the least essential.

Combattant is not a role

 

[Malakhith]

Zoro. No personality after the time skip. His only reason to exist is to participate in shit fights that waste manga pages. If you remove zoro and his opponents from the manga after the time skip, nothing would change, because even his opponents only exist to fight him.
Pre-ts he was actually a good character but now he's just a waste of space.

 

[ShinichiMugi]

For the story,all the SHs after Robin were not really needed. They are great characters anyway.