Hollows who have forcibly removed their mask to gain Shinigami powers. Until recently they were self made but Artificial Arrancars can be made with the Hogyoku. They gain Zanpaku-to's and when released they change their bodies shape and gain powers. They still have masks but they are only partial and they have a human body.

Give your Arrancar's Zanpaku-to a spanish name to fit its powers. Use freedict.com

POWERS:
Bala: Similar to Cero, the user gathers his spiritual pressure into his hand and hardens it and releases it like a bullet, weaker then Cero but 20 faster.

Garganta: Tears a hole in the sky from Hueco Mundo so they may travel to Earth and back.

Sonido: The Arrancar equivalent to Shunpo and Hirenkyaku. Move at extremely fast speeds and is the fastest speed technique.

Hierro: Refers to the hardened skin of the arrancar, which is a result of their compressed spiritual power. While their skin is strong enough to block even released zanpakutō bare-handed, it is by no means impenetrable. Stronger arrancar have proportionally stronger skin.

Grand Rey Cero: A much improved version of Cero and much stronger.

Arrancar Zanpaku-to release: Changes the body of the Arrancar sometimes drastically to give him great new strength. Be creative and think something up.