Several pre-order bonuses for Ground Zeroes will be available in Japan at different stores. One of them gives you special voice samples by voice actors of the game to use as ringtones for your mobile phone.
Here is one sample:
Akio Otsuka (Snake), Tomokazu Sugita (Kaz), Banjo Ginga (Liquid) and Hideyuki Tanaka (Otacon) lent their voices, bundled in several packs: Snake and Miller, Snake and Liquid, Snake and Otacon and Snake and Soldier. The four voice packs will also be available for download on the Japanese PSN store as a bundle.
To hear the other recordings and (Japanese) info on this offer, go to the official website.