Mostly seen in formal letter sign-offs that wish the reader well, such as 顺祺 and 时祺 ('wishing you well'). It is also a popular given-name character because of its auspicious 'good fortune' meaning.
The altar/spirit radical 礻, the left-side form of 示. It marks 祺 as something to do with blessings from heaven, the same family as 福 'fortune' and 祥 'auspicious'.