First Person Pronoun Usage

The First Person Pronoun (一人称) usage means on how every character refers to themselves. The existence of such usage comes from the fact the series' original language is Japanese and it possesses an enormous amount of pronouns if compared to other languages, not only for the First Person, but also for the Second and Third Persons. Thus, how characters use the pronouns of the Japanese language displays an additional layer to the complexity of their personalities. As mentioned before, being this an almost exclusive feature of the Japanese language, this is completely lost when translated into other languages.

Ore
Ore (俺), sometimes written in kana (おれ, オレ)

Ora
Ora (おら)

Watashi
Watashi (私), sometimes written in kana (わたし)

Atashi
Atashi (あたし, アタシ)

Asshi
Asshi (あっし)

Wasshi
Wasshi (わっし)

Vatashi
Vatāshi (ヴァターシ)

Watasu
Watasu (わたす)

Boku
Boku (僕), sometimes written in kana (ぼく)

Washi
Washi (儂), sometimes written in kana (わし)

Wagahai
Wagahai (我輩)

Ware
Ware (我)

Uchi
Uchi (ウチ)

Wai
Wai (わい)

Sessha
Sessha (拙者)

Oidon
Oidon (おいどん)

Achishi
Achishi (あちし)

Achiki
Achiki (あちき)

Trivia

 * In the Vivre Card - One Piece Visual Dictionary, this is translated into English as "The First Person".