It's not usually offered to portray the religious as hypocrites; it's usually offered in response to a believer who says "I can't imagine/it's not possible to not believe in God."
In that case it's highly appropriate to point out, in reply, all of the various and sundry Gods that the speaker already doesn't believe in.
I agree. It is very useful against the argument that to be an atheist requires to first assert the existence of a god, then deny it.
Maybe also can be used if someone asks an atheist for absolute proof, that does not rest on faith, of the non-existence of a supreme being. Or for one who argues that it is impossible to disprove a god.
It can also be used if someone tries to bring up Pascal's Wager, which you can turn around to Zeus vs atheist or Wodin vs atheist to show the ineffectiveness of the argument.
But it isn't a very strong argument for atheism itself. Atheism is the opponent of theism, and so various types of theism are really beside the point. I suppose it is correct to say that a Christian is an atheist towards the Invisible Pink Unicorn (BBHHH), because they are lacking a belief in that deity, but I'm not sure it is a useful argument against Christianity.
Help inform the masses - contribute to the EvoWiki today!
Contributors needed in the following fields: Physical Anthropology, Invertebrate Biology (esp. Lepidopterology), Biochemistry, Population Genetics, Scientific Illustration, Scientific History, Philosophy of Science, Logic and others. Researchers also wanted to source creationist literature references. Register here!
™ Version 4.2