Theists: What is the most compelling argument you have heard for Atheism?

[SteveII]

1. The arguments are not conclusive on their own. They are part of a cumulative argument for the existence of God. Separating them out and positing different entities is an unreasonable step (there is no reason). 

In a cumulative argument, one result is dependent upon the prior result, and so on.  These are all independent lines of evidence: none of them reinforce each other.  What you have is what is known as a 'rope argument' in which the independent strands are woven together to make one argument.  In a rope argument, the whole is only as strong as the strongest individual strand.  And in your case, none of the individual strands are particularly strong or convincing.  So what you actually have is a weak argument.

Perhaps I should have use the phrase "cumulative case".

Regarding the arguments as a group, they are inductive in nature and give a probabilistic conclusion.  I think very few people become a Christian because of the arguments--rather it is an assurance that a belief in God (at least a god) is not irrational and serves as a check against the barrage of atheists shallow challenges to faith being a reasonable thing to hold.