A famous athiest question posed to believers is:

"Could God make a rock so big that he can't move it?"

This is an attempt to put the believer in a logic trap.  If the believer says "Yes", the response is then that makes God to no longer be omnipotent (all powerful) because he would have made a rock he can't overpower.  If the believer says "No", then the response is that God must not be omnipotent if he can't do this.

I want to start this by changing the question to what I believe is really being asked:

"Could God give up his omnipotence?"

I would answer: "Yes."  God could choose to stop being God.  The real question is:

"Would God give up his omnipotence?"

To this I answer: "No."  This is easy because God stays the same.  The logic problem that the athiest is overlooking is that just because a person can do something, doesn't mean that they will do it.  So, the real way to answer the "Unmovable Rock" question is to answer "Yes, but why in the world do you think He would want to do that?"  I would point out that we shouldn't assume that just because God can do anything that He would do anything.  That assumption is nothing short of absurd!  Omipotence is a description of the power that God has, it it does not describe his will.  To find out more about God's will, you can read the bible.  It is His will by which He demonstrates His great love for us.  We were sinners and it was within his power to destroy us, but He gave up his Son to great suffering take our punishment, even the punisment for an athiest.