You don't seem to know what a contradiction is..
If someone says the man was "tall", and someone else says the man was "fat", that is not a contradiction. They are just different bits of information about the same man who is tall AND fat. For it to be a contradiction, one would have to say the man was "tall", and the other would have to say he was "not tall". The two claims need to be mutually exclusive for it to be a contradiction.
Regarding Jesus, all the phrases mentioned in the different gospel accounts were part of his last words. It does not say in any of them that he "didn't" also say the phrases mentioned in other accounts, so there is no "contradiction", no mutual exclusivity. One point you should learn is that the Bible doesn't claim to be exhaustive in its history. The fact that the Bible doesn't mention Jesus going potty doesn't mean that he didn't go potty.
I would recommend that you get Gleason Archers 'encyclopedia of bible difficulties' from amazon or something if you want to see accurate handling of more difficult parts of the Bible, but what you've mentioned here could be answerable by prepubescent Sunday school students.
Also, you ought consider the philosophical principle of charity in your assessment of Christianity and biblical inerrancy: http://philosophy.lander.edu/oriental/charity.html