Go to the Republic Of Dave, which is located in the top right-hand corner of the map. When you first arrive at the front gate, there will be a child that will take you to Dave. After you finish talking to Dave, kill him. Take his key, and use it to open the safe that is next to him. In the safe is a hunting rifle named Ol' Painless. It does 21 damage, but is better than the sniper rifle. It is also a lot easier to repair and find ammo for.