First-person pronoun used mainly by elderly men, often in casual or dialectal speech. Carries a folksy, old-fashioned, or regional feel.
I'm old, so I can't walk that much.
When I was young, there was no such thing.
ぼく is a mild, boyish or modest "I" used by men and boys, in contrast to わし's old-man, folksy tone.
Standard kana spelling; the word is usually written in kana.
Kanji form; rarely used in modern writing.
Katakana spelling, sometimes used for stylistic effect or in manga.
Ateji-like kanji form; rarely used and easily confused with わたし.
Derived from 私 (わたし) through sound change. The exact historical development is uncertain, but it has been used as a first-person pronoun since at least the Edo period.