First you have to come up with a definition of "God".
Every major traditional god that has been defined has been dis-proven already, people just don't want to accept the proofs.
Disproving gods isn't so much a matter of science as it is a matter of history, anthropology, archeology, and science.
If you are talking about the "god of Abraham" in particular, then archeology shows that the entire Torah (first 5 books of the "Old Testament") was written in the 7th century BCE, some 1000 years after its is traditionally dated, and that none of the events in the Torah really happened. The whole conquest of Canaan never happened, indeed many of the places that the Jews are said to have conquered during the conquest of the holy land didn't even exist at the time in which the stories are set. The evidence is against the existence of Moses, against Jews ever having been slaves in Egypt, etc., etc.
When we look at the god of the Jews, its clear that this "god" is simply an explanation for natural events. Its why the god of the Jews seems so horrible, because nature is horrible. For example the god of the Jews used collective punishment, punishing whole populations for the "sins" of a few, and punishing later generations for the "sins of the fathers". Well this is because natural disasters are indiscriminate, and they affect everyone. The Jews interpreted natural disasters and wars and punishments from their god, as many ancient cultures did.
If you believe that famines and plagues and wars are caused by your god as punishment, then its logical to believe that your god punished whole cities and whole nations for the sins of a few, since obviously every single person isn't horrible and deserving of punishment.
So, it can be proved that specific claims made in the holy texts of any religion either never happened, or cannot be true.
Now the "Christian god" is interestingly one of the easiest to disprove due to the relatively large volume of literature from prior to and around the time of the origin of the religion.
For example it can be shown that the concept of heaven in Christianity comes from Plato, the concept of hell comes from the pagan Tartarus (which is actually the word used in the Gospels for "hell"), and as I put forward here, that the entirety of the Gospel stories started out as a fictional allegorical story, and that every scene is really based on literary allusions, and thus never really happened:
So, its not so much that "God" can be disproven, its that any meaningful specific definition of a "god" can be disproven.
Its possible to come up with definitions of gods that can't be disproven, but those definitions are meaningless. If a god is an undetectable being with no influence on the world, then its not a meaningful concept, and of course if a god is undetectable being with no influence on the world, then it can't be the same being that spawned any religion, because such a god would never have been known to anyone.
I don't believe God can technically be 'disproven'. As is mentioned below, neither have unicorns, leprechauns, or fairies been disproven, but we know that their existence is highly unlikely, ranging on virtually impossible. Of course, we said that about the colossal squid described by sailors in the pirating centuries, and voila, we found one. But the fact is that these do not click with science at all. It's hard to explain but I think they're as disproven as they're ever going to be, because how can you disprove something that's absent except in the fact it's absent? Yet there is the Christian argument of 'oh he's all around you all the time!'. . . it's not something you can scientifically measure. Whether God exists or not IS a scientific question, but I don't think it's one that will ever officially be answered. Not that it matters, like I said; I consider the theory disproven in my own eyes already.
you really seem like a smart person, oh what the heck i should give it to you, you are smart.well i'm not waste time i'll just qoute a passage from th word of god. " for the children of this world are in their generation wiser than the children of light". because i really don't want to debate you i'll just hit you with another passage."For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God. (1 Corinthians 1:18 )."jesus said you all looking for a sign but there will be none except that of jonah". you all looking in the wrong places.
If you realized it's origin (/b/), you would accept it's awesomeness!
Sometimes the point made is what's relevant, and the purposely added grammatical errors just further enhance it. To point out such errors, you would be considered a "newfag" (although it has nothing to do with homosexuality) and I would be called captain obvious or obviousfag, for obvious reasons.