Many weak atheist reject being called an agnostic and many agnostics refuse to be placed in the atheistic category. Regardless, all who profess to be weak atheists are in fact agnostic and agnosticism falls within the realm of an atheistic worldview. This leads to reasoning that agnostics generically argue that they don't believe in divinity for lack of proof, but there aren't any Christian agnostics. If an agnostic holds onto a religious belief, then the agnostic is a theist and doesn't believe in the non-existence of god due to a lack of proof (those who do believe in divinity and still are agnostic are really undeceive theists). They are therefore either theists or atheists.
Within the realm of agnosticism, there are a few viewpoints in which one can cling to and each one poses its challenges to the Christian apologist.
Hard agnosticism claims that the existence of divinity is unknowable. Knowledge to the hard agnostic can only be obtained through personal experience of the natural world and anything beyond the natural realm cannot be comprehended. The argument against a hard agnostic stance is that one must have some knowledge of divine nature to make a claim about the properties of the divine. Knowledge of the divine is a prerequisite of knowing that it is unknowable.
Empirical agnosticism views divinity as not known but not unknowable. The empirical or soft agnostic argues that there isn't enough evidence to support or deny the existence of divinity. There usually two type of people who hold this standpoint; those who honestly don't know but want to and those who are apathetic to the divine (not to be confused with Apathetic Agnosticism).
The first group of people are hard to come across. The Bible says that those who are looking for God will find Him. The second group, however, is usually the everyday self-proclaimed agnostic. The empirical agnostic is presented with a choice. Wait for evidence that might not happen in our lifetimes, or make a concrete decision for or against other worldviews based on what is already known. A soft agnostic stance is usually taken by those who, not because of a lack of evidence but because of lifestyle implications, would rather choose not to choose.