First person: Ore
Iwaizumi → Iwa-chan
Matsukawa → Mattsun
Hanamaki → Makki
you → you-chan (May also give a nickname based on a feature. e.g., if you has brown hair, then Brown-hair-chan, etc.)
Speech style: "~ jan," "~ janai?", "~ desho," "~ mitai," etc.

First person pronoun: Ore
Oikawa → Kuso-kawa, Kuzu-kawa, Unko yarou, Oikawa
Hanamaki → Hanamaki
Matsukawa → Matsukawa
you → you

First person: I (ore)
Oikawa → Oikawa, Crappykawa (occasionally)
Iwaizumi → Iwaizumi
Hanamaki → Hanamaki, Hana
you → you

First person pronoun: Ore
Oikawa → Oikawa, Kuso-kawa (occasionally)
Iwaizumi → Iwaizumi
Matsukawa → Matsukawa, Mattsun (occasionally)
you → you