OniGiri is Japanese For Rice Ball
A Rice ball is a Triangular shaped Ball of Rice with a Seaweed wrap.
Though, with there name, they can actually take the Shape of a Rice "Ball"
People Tend to take ingredients and make them into Japanese Characters. 
They can come in many shapes and sizes.
Here is Pikachu cosplayed as a rice ball:
Oh right! Rice balls can also have many different ingredients in it, Here is an example of one with Chicken in it: 
Here is a Salmon one: 
And they can be coated: Here is a Bread coated one: 
They are made with more then white rice though: 
