My favourite is when an atheist tries to quote the Bible and completely fails. Found a bible passage about smashing babies on rocks? Let's now read the context. THEY (the Babylonians, who incidentally weren't following God's law at the time) did that to US (Israel). The song is a song of mourning and loss, and imagined revenge, as if that would make it better (it doesn't), but it isn't sanctioned, so we can't.
So how exactly is that a counterargument to God being good? Or am I bashing my head against a brick wall here, talking to an atheist with unshakeable blind faith in his demonstrably incorrect position.