The "pizza" argument against the existence of an all-powerful being goes something like this:
Suppose for a contradiction that there exists an all-powerful being. Then there cannot exist a pizza so big, that He cannot eat it. Therefore, this being cannot create a pizza so big, that He cannot eat it. Therefore, there exists something that this being cannot do. Therefore, this being is not all-powerful, a contradiction.
I don't like calling this the "pizza argument", since it really has nothing to do with pizza. What is this argument actually called?