Atheists, what are the most convincing theist arguments you heard of?

[Neo-Scholastic]

The argument in a better form, states that everything that begins to exist, has a cause...the argument does not say that everything requires a cause; only that which begins to exist. 

That's true enough, but that formulation at least appears to beg the question. The qualifier "begins to exist" already implies something that didn't begin to exist, which is the conclusion of the argument, i.e. there must be something that did not begin to exist. Also it doesn't establish that the thing that didn't begin to exist has any causal power. I'm not saying those are fatal flaws, but it is enough ambiguity to justifies skepticism. Personally, I think the 1W of Aquinas avoids both these problems since it relies on an already established continuum between potential and actual existence - taken from Aristotle's Metaphysics Zeta. I suppose the notion of "beginning to exist" could be derived from Aristotle although I haven't looked into that possibility.