Acquire the Melee Throw Skill. Collect or purchase the most powerful weapons that you can find. Travel to a location that is safe from enemies. Use the Melee Throw Skill to throw your weapon at a wall. Immediately after the throw, open the menu, and the same weapon will also appear there. Drop the one from your inventory. You will now have two of the same weapons that can be collected, one that was thrown and one that was dropped. Pick up the weapon again and throw it. Repeat the process as many times as desired to duplicate the weapon. Then, sell the extras for money.