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

[masterofpuppets]

And the First Way of Thomas Aquinas:

1. It is certain, and evident to our senses, that some things are in motion.
   
2. Now whatever is moved is moved by another.
   
3. If that by which it is moved be itself moved, then this also must needs to be moved by another, and that by another again.
   
4. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover, seeing that subsequent movers move only inasmuch as they are moved by the first mover: as the staff moves only because it is moved by the hand.
   
5. Therefore it is necessary to arrive at a first mover, moved by no other; and this everyone understands to be God.
   

Both ultimately fail because their basic premise is bare assertion. The need for a cause can only be established to hold within the universe itself; asserting that there is a need for a cause for the universe itself is an unsupported assertion...

No premise in the 1W refers to the universe, does it? You're reading into the demonstration something that isn't there.

The argument ultimately concludes that phenomena within our Universe apply to the Universe as a whole. Things within our Universe need a first mover, and only things within our Universe. This first mover was the Big Bang. However, you cannot demonstrate that the Big Bang itself requires a first mover.

The argument ultimately fails because you can replace the last sentence with "this everyone understands to be the Big Bang" and actually come up with a better argument.