I would like to argue that one of the most common complaints of the skeptic might also be one of the most foolish -- "If God wanted to get me to believe, then He could do so very easily by just doing...'X'."
The problem with this statement is that it is impossible to know whether or not the occurrence of "X" would ACTUALLY cause the skeptic to believe. For instance, let us substitute 3 different scenarios in for "X".
"If God wanted to get me to believe then he could do so very easily by just...."
1. "Bringing my brother back from the dead."
2. "Appearing physically in Time Square."
3. "Causing 40 days of darkness upon my request."
I want to go through these one by one and argue why I think it would be foolish to ASSUME that the occurrence of any these miracles would ACTUALLY guarantee the skeptic coming to belief in God.
1. The skeptic is visited by his resurrected brother. His first thought will almost certainly be "How is this possible?" At this point, he will search for any way of explaining the phenomenon without accepting the miraculous. He will find multiple possible (although improbable) explanations. For example, it is possible that his brother elaborately faked his own death. It is also possible that his brother had a secret identical twin. Even more improbable, but still possible, is that someone could have gotten extensive plastic surgery, learned to impersonate his brother and studied important minutia about his life to seem convincing.
2. The first problem with God appearing physically is that we wouldn't necessarily know what to look for. Would He be in human form or would He manifest Himself in another way? A burning bush would be quickly dismissed nowadays as special effects. On a related note, the second problem is that no matter where He might appear, only the people who were there could say that they actually witnessed it. And even if you had thousands of people saying that they saw Him and something caught on video tape, there would always be an overwhelming majority of the human race (billions of people) that weren't there and would be very skeptical of such evidence in the age of computer generated effects and of tremendous illusions performed in public.
3. The third scenario seems to me like it would be the easiest for the skeptic to dismiss. Amazing coincidence? Sure. Miracle from God? Doubtful. Since it involves a natural phenomenon, there would inevitably be an abundance of scientific explanations (no matter how contrived) for the event in question.
Now, to be fair, I could envision this argument easily being turned on it's head. For instance, a skeptic might say that the only reasonable Theist is one willing to say, "If 'X' happened then I would no longer believe in God." From that point the skeptic could argue that nothing substituted for "X" would ever guarantee that the Theist would abandon their faith. It is just as likely that they would try to find ways to explain it that allow them to maintain belief in God. However, while this inverted version of the original argument may serve highlight the foolishness of many forms of Theism, I think it fails against Christianity because the Christian claims to have "properly basic" evidence for God based on experience of Him. But that opens up an entirely different discussion.
So, just to wrap up, I think that this argument demonstrates the foolishness of a very common complaint raised by skeptics. Furthermore, by turning the argument on it's head it can be observed that both sides who would seek to maintain their point of view against proposed evidence (empirical, philosophical, hypothetical or otherwise) are ultimately doing so based on faith.