Gyah

Basically when a little anime loli fucker says it when they're taunting a male AKA a Otaku. A great representation can be seen in the manga. "Don't Bully Me Nagatoro." You find this in Chapter 12. It is sorta used the same as fufufu, which is like a cute evil anime laugh. Can also be interpret as a sort of gasp.

Otaku Based Faggot - "Please leave me alone Miss."
Anime loli fucker - "Why don't you make me? Gyah, Gyah, Gyah.