The dumbest "arguement" I have heard was someone telling me that I don't really know the facts... as if the Bible were full of facts.

"The second law of thermodynamics says that we have to have been created by God (specifically the Christian God mind you) and that is why abortion is bad."

"You must be angry at God"
"It's illogical that you point out illogic in something you say you don't believe."
"The universe IS evidence of God; just look around."

One of my favorites is atheism is a religion.
That's like saying not shooting up heroin is an addiction.

I always find the line that atheists cannot be moral or ethical to be the most silly.

"But they found Noah's Ark!"

'Where?'

"....."

"Atheists just like to sin."
"Without belief in God, you can't have morals."
"You'll see you were wrong when you're burning in hell."
"Atheists don't believe in anything."
"Science will prove God."
"I didn't take religion seriously when I was younger, either; you'll come around."

I’m not sure I understand the question.