Can you duplicate in fallout new Vegas?

Answer 1

Only Certain Items. You can use the scrap metal glitch to duplicate scrap metal by continually selling to Casdin. You can also duplicate any "throw" weapon (mines, grenades, etc). You can also duplicate Caps (if you have at least 35000 in your inventory) with the cabnet in your house. The caps glitch may have been fixed so if you want to do it on the xbox you will need to clear your cache.

There is a fairly detailed explaination of the scrap metal giltch at (how to and why it works):

http://www.ngook.com/archives/140

And a video that explains the Mine duplication in detail at:

http://www.YouTube.com/watch?v=36erAyjBnRM

Duplicate Caps Glitch demonstrated at:

http://www.youtube.com/watch?v=Y8UbbitrwKw