Do you claim to KNOW that God exists?

If so, then what is that supposed knowledge based on? Personal experience is notoriously subjective and not reliably trustworthy. Claiming to know because of the revelation of scripture only moves the question back a step, because then it's a question of how you KNOW that your particular scripture really was the one true revelation that actually came from God. Or, to say that you know God exists because of creation itself is just an Argument from Ignorance. So how do you really KNOW?

If you don't believe the Bible is wholly inerrant...

How do tell which parts of it are the message from God and which parts are just fallible humans getting it wrong? Don't you have to just use your own human sense of morality to judge which moral pronouncements seem like they came from God, and your own understanding of human science to judge which of the claims about the physical world are accurate? What value does a supposed message from God even have if you have to do that?

Why does God care so much about being worshipped?

I don't consider it a satisfying answer if you just say how he's worthy of worship. That is an arguable claim in itself, but it still doesn't explain why he cares so much about being worshipped, to the extent that it's considered a moral failing if you don't. How is that not extremely narcissistic?

Is something more wrong based on how much it hurts somebody?

...Or is the extent to which it does or does not please God the one and only factor that affects how wrong something is?

If God told you to kill your son, would you do it?

You can't say that God would never do that, because he already did do it to Abraham. Sure, you can argue that was a special case, but the precedent is there.

Alternately, if someone else told you that God had told them to kill their son, what Biblical argument could you use to change their minds? What possible appeal could you make, from the standpoint of religiously-driven morality, that would trump a person’s sincere belief that God had spoken to them?

What effect do you believe prayer has?

If you hold the position that “prayer doesn’t change God, prayer changes me,” then aren’t you basically saying that a practice which is purported to be communication with the One True God is effectively the same as any other form of meditation?

But if you hold the position that praying for something can actually change the outcome of real events from what they otherwise would’ve been, then how can God have a perfect plan for the world when his plan can be easily uprooted any time somebody prays?

The Westboro Baptist Church challenge

Can you name any doctrine the Westboro Baptist Church holds that doesn't have scriptural support? And it doesn't count as not being scriptural just because you disagree with their interpretation of scripture (for instance, WBC is Calvinist; if you're not Calvinist, that doesn't mean Calvinism doesn't have any scriptural support). Also, it might help to check their FAQ before assuming they haven't thought about the scriptural reasons for one of their beliefs.