
Mainly, we fight about the nature/attributes of god: has a thousand arms, is found in the sea, is found in the air, is found in a burning bush, throws thunderbolts, was crucified, is male, is female, is genderless, carries a large hammer, enjoys drinking blood, has a long white beard, is wrathful and jealous, likes a good flood, etc.
The attributes of deity are many and various, if not infinite. Some people say that all attributes are manifest in deity, and therein lies an opportunity. If everyone agreed that all attributes are the attributes of deity, then we would have no basis for disagreement about the nature of deity. (And by the way, having all attributes is equivalent to having no attributes.)