Argument from ignorance is an extraordinarily common argument for believing in a god. One of the most common ways to invoke it is to try to make the skeptic admit that they don't know something, and from there to jump to god, and to declare victory. In some cases the argument from ignorance is masqueraded as something else by using complex philosophical terminology and phrasings.
However, there's a popular form of this argument that's unusually blatant. Rather than trying to masquerade or hide the actual argument from ignorance, it's actually fully embraced and stated openly.
It goes something like: "If this (often a large circle, or alluding to everything that's possible to know) is everything that can be known, and this (a very small portion, eg. a small dot or percentage) is what we currently know, isn't it possible that God exists in the rest that we do not know?"
That is, rather than trying to hide, masquerade or obfuscate the argument from ignorance, just blast it fully open and outright state it. The big irony is that many people who present this argument seem to think that it's such a clever and outstanding argument, that no skeptic or atheist can respond to it.
For example, in this video a preacher lays out this very argument. He takes a long time to get to it, but the actual argument starts at about 4:30. (After he states the argument the audience laughs. I would like to think that they were laughing at the ridiculousness of the argument. Sadly, that was most likely not the case.)
(Quite ironically he says a bit before that: "and the Lord gave me an answer that I had never thought about until that moment." If such a blatant argument from ignorance is the best that the "Lord" can come up with, he isn't very smart, I would say.)
Of course the major problem with this argument is that it can be used to argue for the existence of anything you want. Dragons, unicorns, fairies, multiple gods, evil gods, the god of any religion, gods of no existing religion... whatever you want. (Ironically, the exact same argument could be used to argue for the non-existence of any god. You could just say "wouldn't it be possible that in that 95% that we don't know there is no god, and instead there is the explanation for everything without any god?")
But why would anyone believe in their existence without any actual evidence? You don't believe in everything just because there might be a remote possibility that it exists in that gap of knowledge. Rational people require actual evidence before believing in such extraordinary things. Believing in things without any evidence, just to fill out gaps in knowledge with hypotheticals, is most certainly not the smart thing to do.