The two accounts of the death of Judas Iscariot are directly contradictory. Here's Matthew 27:5:
And here's Acts 1:18:
It's just about possible to say that Judas hanged himself and then the rope snapped and he fell onto the field. Another explanation is that his hanging attempt was not successful (though Matthew surely expected his readers to understand that it was).
Did he throw the silver away or use it to buy a field? This is as blatant as contradictions come.
I suppose a hardcore infallibilist will say that "the reward of his wickedness" does not refer to the silver he received for betraying Jesus. But no honest reader of Acts will conclude that it means anything else.
Alternatively, a reader of this page notes that Matthew 27:6-8 has the priests of the temple buy a field with the money, and suggests that this means, by extension, that Judas "acquired the field". This is stretching the normal meanings of words beyond credibility, but is the sort of move the doctrine of infallibilism requires.