Note: You will need a few C4 and a Detonator for this exploit. In the final part of the game you will enter a vault with 37 gold bars weighing 35 pounds each. Each gold bar is worth 10.539 caps. Clearly you can not take them all -- unless you use this exploit.
Enter the vault and the door will seal behind you. Take everything in the room that you want to including the 36 gold bars on the table to your right and the 1 gold bar on the overseers desk. Deactivate the security system and activate the computer on the desk. IMPORTANT: Only read "Vera", DO NOT access the file that shows up after you read it. Elijah will appear on the monitor, convince him to meet you in the vault. When the conversation ends leave the room immediately (it unlocks), and walk to the far right stairway. A blue force field will appear blocking your path, lay your C4 at the bottom of those stairs and then press your body against the blue force field in the doorway. When Elijah finishes speaking, for some reason you and he switch places. (You'll see what I mean) Make sure he is on or very near your C4. Detonate and leave the way you came. Congratulations you now have 37 Gold Bars worth a total of 389.943 Caps.