My previous post was aimed at just about everyone rather than at religious or spiritual people in particular, as almost all humans have children, or believe that life is a 'gift.' I think that, because of how broad the scope of those to whom that post applies is, it's much more relevant to our society than this one (especially when you realize that technology has now superseded god, anyway), but the god premise is generally easy to repudiate, so let's give it a shot.
God is omnipotent
1. If god is omnipotent, then he/it should be able to create anything imaginable -- even if a given thing were to fail to adhere to the laws of logic and physics, like circular triangles. Otherwise, he/it would be limited in his/its power.
2. We can imagine a god more powerful than god.
3. ...But if a god more powerful than god were to be created by god, then he/it wouldn't be omnipotent, as the new god could kill him/it or otherwise will him/it out of existence.
4. ...But if a god more powerful than god is impossible, then god is not omnipotent.
5. Therefore, god does not exist.
God explains the complexity of the universe, or is entailed by it
1. The universe is a beauteous, grand, and extraordinarily complex* place.
2. Beauteous, grand, and extraordinarily complex places have to be designed or otherwise created by someone. How could they grow to such complexity without an entity of some kind behind their orchestration?
3. ...But god is far more -- infinitely more, in fact -- complex, grand, and beauteous than our humble little universe.
4. Therefore, god would require an even more complex creator in order to explain his/its own existence, ad infinitum.
5. Therefore, god does not exist -- or is at least superfluous and non-functional, given the law of parsimony.
* I disagree with this premise, because there is nothing against which we can relatively compare the universe. Therefore, the universe is neither ordinary nor extraordinary; it merely is -- for now.