The best rendition of it is by J.L. Mackie, in an essay entitled “Evil and Omnipotence” published in Mind back in 1955. It is superb, and still very hard to best. The basic idea is that there seems to be something paradoxical about the very concept of omnipotence, which may indicate that the idea of omnipotency is intrinsically incoherent.

The argument is usually presented as a variant of the following: can an omnipotent god create a mountain that he cannot move? If you answer “yes,” it looks like god can do something that he cannot undo, which means that he is not, after all, omnipotent. If you respond “no” then you are immediately acknowledging a limit to what god can do, so again it turns out that he is not omnipotent. Try getting out of it, you’ll either laugh all the way to your logic class (if you are an atheist) or get a really bad headache (if you are a theist). (The funniest variation of the paradox is due to that immortal philosopher, Homer Simpson: “Could Jesus microwave a burrito so hot that he himself could not eat it?”)

just noticed that part, that’s a great paradox, one for the pub me thinks.