The Character Died with Him: Kaneto Shiozawa, the original voice actor for Zato-1, died from injuries sustained in a tragic accident. After that, Zato "died" and his body was taken over by Eddie and he has been voiced by Takehito Koyasu... until Xrd, when he suddenly went back to being Zato-1, and still with Koyasu as the voice actor.
So far, Baiken has three. The original one, used exclusively in The Missing Link was Satomi Koorogi (the voice of May), who previously was the voice of Sakura (but not Mayo Suzukaze, who voiced the actual Kenshin Himura, off whom Baiken was based). The second one is Sudo Miho, whose deep voice acting was used in a good portion of Guilty Gear games, at least up until Accent Core, which had Chizu Yonemoto instead.
Potemkin originally was Hideyuki Anbe. From Guilty Gear X and onwards, he is voiced by Takashi Kondo.
Chipp Zanuff has three. The original one, used exclusively in The Missing Link was Takuya Morito. The second one is Takeshi Miura, who was from X all the way to Accent Core. In Xrd, he is now voiced by Yoshihisa Kawahara.
Kliff Undersn was originally voiced by Hatsuaki Takami. From X onwards he is voiced by Shigeru Sakano.
Justice has three. The original one, used exclusively in The Missing Link was Takuya Morito. In XX she is voiced by Yumiko Ogawa. The third, Wakana Sakuraba, only voices her in the Accent Core Plus story mode.