an auxiliary adjective attached to the masu-stem of a verb to express desire: 'want to ...' or 'would like to ...'.
私は寿司を食べたい。
I want to eat sushi.
来年はもっと旅行したいと思っている。
I intend to travel more next year.
彼女はピアノが上手になりたいと言った。
She said she wants to become good at piano.
a sentence-final particle in Kyushu dialect used for emphasis or assertion (regional usage, similar to 'yo' or 'ぞ' in nuance).
そんなこと、あり得んたい！
That can't be true, I tell you!
早く来なさいたい。
Come quickly (emphatic, Kyushu dialect).
a suffixal/adjectival use forming adjectives meaning 'very ...' or 'worthy of praise' in older or dialectal forms (e.g., the adjective めでたい).
そのニュースは本当にめでたい。
That news is truly joyful/auspicious.