Batsu Ichimonji from Rival Schools, Alisa Bosconovitch from Tekken, and Vashyron from End of Eternity are playable characters in Project X Zone. Famitsu also confirmed Neneko and Neito from the PS2 game Yumeria.
Juri from Street Fighter IV shows up in Project X Zone as a crossover rival character. Jedah Dohma (Darkstalkers), Heihachi Mishima (Tekken) and Aya-me (Sakura Wars) are also borrowed bad guys.
Project X Zone comes out on October 11 for Nintendo 3DS.
Update: Scans from Famitsu show Riemsianne La Vaes from Shining Force EXA, Seth from Street Fighter IV, and Skeith from .hack in Project X Zone as rival characters too.