The set of issues usually entitled "God and morality" is at the metaethical level. This includes a difficulty (the Euthyphro problem), an argument for the existence of God (the argument from morality) and just a really interesting set of questions about the relationship between God and morality.
There is, however, also a set of issues at the normative and applied levels largely independent of the metaethical level. Whatever the metaethical story of the relationship between God and the truth of moral propositions, one can ask about any particular rule at the normative level or any particular ethical judgments at the applied level whether the particular ethical truth in a special way depends on the existence of God.
To see that this question is in large part independent of the metaethical one, take a trivial case at the applied level: the duty to thank God for our lives. This is indeed a moral duty, and it depends on the existence of God in a special way: namely, we need to thank God for our lives because God exists and has created us. This is true if the right meta-ethics makes no reference to God, as in the Kantian case--there still is a general duty to be grateful to our benefactors, and we can apply this to the case of God creating us. And this may well be true even if the right meta-ethics makes reference to God, as in the divine command theory case--God commands the general principle to be grateful to our benefactors; in this case, our benefactor is God, so the duty to thank him depends in a special or additional way on the existence of God.
The interesting question, of course, is about moral duties that do not make explicit reference to God. Do some of these moral duties presuppose the existence of God? If so, then they give rise to arguments for the existence of God, though the atheist might just deny the existence of the duty.
So let me open this up for discussion--what moral duties are there that, although they do not say so on their face, in fact depend on the existence of God?
Note: It might seem that such special claims of dependence are incompatible with the idea of ethics not being dependent on revelation. But that problem is only there if both (a) the belief in the existence of God requires revelation and (b) our knowledge of these ethical claims requires a belief in the existence of God (the truth of the claim may depend on the existence of God, but it does not follow that the claim epistemically depends on the claim that God exists, just as the truth of there being a rainbow depends on facts about refraction of light, but the claim that there is a rainbow does not epistemically depend on claims about refraction of light, being independently knowable).
As a warmup, let me suggest this one: Is it the case that the duty to love everybody depends on the existence of God, e.g., because only if everybody is in the image of God, or only if everybody is loved by God, is it the case that everybody is lovable.