Can God make a rock that He can't lift?
Think carefully before you answer that. We, as Christians, often claim that God is omnipotent - that is, we say He can do everything, and so to state that He can't lift a rock seems utterly impossible. This is, however, nonsense. God is all powerful, but that is not the same as being able to do everything.
Let us put this more plainly. Christ himself remarked that he neither knew the day nor hour at which his return would come. Yet this very same Christ claimed to be God - the same omnipotent, omniscient God of the Old Testament. If Christ is The All-knowing God, then would He not know everything, including the details of his own return? This presents a problem, but only for a moment.
Should we say that God can create a rock which He cannot lift? Let us assume that, yes, He can. If so, it is not God's weakness on display if He fails to lift the rock. Rather, it is His power to limit His own abilities that reveals His own omnipotence. It is not a weakness that Christ - God in human flesh - does not know the details of his own return. Rather, it is a display of his omnipotence that he can determine whether or not he knows those details.
Is it really all the impressive that God can lift every rock on planet earth? Is it not much more impressive that He can control whether or not He can lift that rock? Is that not, then, the very definition of being "all-powerful"? To do everything, and to be able to control whether or not one can do everything, are vastly different ideas. In one version of the universe, one may do everything, but one does not necessarily have control. Who, would we say, has more freedom and control: the man who can drink beer after beer until he is falling down drunk, or the man who can control whether or not he drinks more than one beer (or, indeed, any alcohol at all)? The one who says, "I can, but I believe I won't" has more control, does he not?
God is much the same way. To say that "He cannot lift a rock" is to deny His omnipotence. To say, however, that "He can choose whether or not He can lift a rock" takes the power and puts it in His hands. And that, really, is what He asks of us: to choose to let Him live through us. One may argue, then, that choosing Christ is not a sign of weakness, but, in fact, complete submission to him may be our greatest moment of strength.