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わたし　わたくし　ぼく　おれ watashi, watakushi, boku, ore

私　わたし　watashi (formal)
私　わたくし　watakushi (very formal, business like)
僕　ぼく　boku (generally young boys, but some adult use as a style)
俺　おれ　ore (very casual, male language)