Reading the Bible.
I flipped mine open at random (yes, I swear it) and found Ezekiel 33, which reads as follows:
The word of the Lord came to me: O Mortal, speak to your people and say to them, If I bring the sword upon a land, and the people of the land take one of their number as their sentinel; and if the sentinel sees the sword coming upon the land and blows the trumpet and warns the people; then if any who hear the sound of the trumpet do not take warning, and the sword comes and takes them away, their blood shall be upon their own heads.
It was texts like these that most likely got John Brown's ire up when he thought about millions of American slaves held in suffering. Perhaps we could have prevented the Harper's Ferry incident by clipping verses like these out of all Bibles in circulation at the time.
In all seriousness, the readiness to blame works of art (that is what video games are) for real violence has many historical precedents but has never made an iota of sense.