At the Code Input Screen enter the following codes:
Grab a civilian and go to the top of a tall building. Press Triangle and wait a moment. They will try to run away, but fall off the building.
In the badlands area, if you pick up a cow you can use it an unlimited amount of times as a bludgeon that will never break.
Kill a civilian, and just before the civilian dissapears pick the civilian up (B) and then put the civilian down (Y) and it will be alive and walking around again.