We all know how frustrating arguing with a theist can be. They are just really bad at reasoning through an argument, or sometimes, they are actually so good at it that it defies our ability to understand why they can't (in general, don't want to) see the force of our arguments. But the agnostic can be especially frustrating in their own way. They generally do not argue for any particular position, they simply stand back and pick apart everyone else's arguments. In this way they set themselves up as the "rational" party, the one's who "just demand a higher degree of evidence" or certitude before they grant us the pleasure of their consent. With the theist, at least, we know where they stand, and we can condemn them for their willing ignorance or their obviously bad arguments, but be satisfied afterwards that we have a clear advantage over them in clarity and coherence of our own viewpoint (that of the truth!). But the agnostic is particularly infuriating because they take skepticism and run with it. They argue that truth is something which is hard to come by (true enough), and in the case of deities there simply isn't enough evidence to back up the claim that they do or do not exist. Wrong! Belief in deities is just as silly and absurd as belief in any other hypothetical nonsense, like trolls or fairies or hobgoblins, unicorns, leprechauns, ghosts, superheroes/supervillians, dwarves, elves, Nasgul, orcs, Cauldron-born, talking animals, ogres, witches, wizards, warlocks, dementors, etc., ad nauseum. The entire realm of magical and supernatural beings and their "powers" falls into the same class, and no specific deity is granted some special privilege or right to a degree of doubt about their non-existence as any other. If you rule one in, you rule them ALL in. And let's not forget that Yahweh has a host of angels in his "kingly court" as well, not least of which was Satan. There seems to be no single reason why we should entertain the idea of creator-deities and their prophets, nor distinguish "ours" (Yahweh/Jehova) from any of the other ones which have existed in the minds of men throughout history. Why not Uranus and Gaia, or Tiamat and Marduk, or Enlil the "father of the gods" in the epic of Gilgamesh, or Amon-Ra? So here's the thing, agnostics: shit or get off the pot. If you don't know what to believe, then have the courage to settle the matter for yourselves, because agnosticism is not a mature position to take. It is a resting point on the road to having some actual convictions about the way the world really is, and what it means to be rational or not. Do you think it is rational to believe that there could really be a Zamp in the lamp, or a Woset in the closet? What is the substantial difference between the whole host of supernatural beings and the Wocket in my pocket?
It is really easy to sit back and remain uncommitted to any particular belief, but at some point we all have to decide whether to believe in evolution, or global warming, or what our own sexual orientation is, or a million other things that are relevant to how we decide to live our lives. If you approach a topic of which you are ignorant, then just say you really aren't sure, you don't know all the arguments, you don't have all the information. You're still trying to figure it all out, still trying to make sense of things. But don't sit there and say that suspending judgment is really the only rational conclusion we can reach about what kinds of things are real and what kinds of things are fantastical and imaginary. It's not sophisticated to claim that there is any merit to looking at the world from a supernatural perspective, it's just annoying, and in my opinion, cowardly.
At least the theists stand for something. Agnostics only stand up for the idea that we can't know anything. Skepticism is great, but only up to a point. After that, it means you have no convictions.
There are certain things we know to be incomprehensible; either they do not exist, or possibly exists outside of the confines of which we derive knowledge. For example, we cannot know what would have happened if something didn't happen, what something looks like that doesn't exist, the ramifications of an infinite quality, or the existence of God. To illustrate, let's run through several definitions of what God could be, and why they are incomprehensible.
God is all-powerful. All-powerful implies infinite power; however, anything that a manifestation of God shows us must be finite, so we could always ask, "What's more?" And an all-powerful God would have to show us more, ad infinitum, and still never prove that it is all-powerful.
God is all-good. Firstly, if what is "good" is defined by God, then this begs the question. If "good" was a discrete quality found in nature, then it isn't so impressive; even more so, it would be contradictory to his supposed omnipotence if he could be confined within natural properties. We haven't found "good" to be a natural property, and therefore goodness is either incomprehensible in itself, or relative and not absolute, and therefore all-goodness would be incomprehensible.
God created the universe. If God created the universe by laws of physics, then it is a task that could be reproduced without God if all the conditions were known and met. Therefore, that a being created the universe would not be such a unique quality. If God created the universe whimsically, which most interpretations of God entail, then it cannot be understood that he did. More on this later.
God is free from the laws of nature. Since all human knowledge is either empirically inducted (e.g. science) or logically deducted from analytical facts we consider that we know to be true, it is impossible to comprehend the concept of an all-powerful God that defies axioms of which we base all our knowledge. And if such a being were to appear before our eyes in whatever form it pleases and conjure any imaginable object, in such a way that it significantly contradicts what we've come to know, if it alters all physical properties, changes our senses, and creates new perceptions of consciousness, then we must really question whether we know anything at all before we consider the existence of that being. It would be strange to use logic that have been defeated, or depend on perceptions which have been whimsically altered without our perceived control, to claim to "know" that God is the only objective truth. Why should one have faith in his logic and perceptions at all to make such a judgment?
We should worship God. Whenever an imperative is given, a goal should also be given. Even if an all-powerful being exists, why should we worship it? Even if it is all-good, why should we strive to be good? As people with reasoning capacity, most of us are not simple hedonists, and so the heaven and hell justification doesn't suffice. Nor can anyone convince me that longevity of life is a categorical imperative, because if you don't worship God, he will kill you or torture you. In fact, I categorically reject all categorical imperatives (sorry Kant).