As a Korean, I have my two cents:
Since "ki" is a syllable derived from the addition of the "k" consonant and the "i" ("ee" as in "leer," "leet," "leek") vowel sounds (き + い = きor whatever, that shit), I'd say that it's pronounced as "KEEEEE" more than anything.
But that's just a Korean talking.
카이
키
수
캐
see: Wiki's Hiragana Table
edit: Everyone knows Japanese people are only capable of hiragana syllable pronunciations ;p