Where can I find the Fat Man in Fallout New Vegas?

Solution 1:

Well, merchants don't charge different prices, so the only way to lower the price of an item is to increase your Barter skill.

You can find Fat Men in the following locations (source):

• Cottonwood crater - On the body of a dead prospector.
• Quarry Junction - Lying near the edge of a radioactive pool to the west of the quarry. On this map you can select weapons>big guns and you will see 3 markers on the map,one of them is the location for the fat man(Quarry).
• Nopah cave - On the corpse of a super mutant master.
• On the body of a super mutant master near a cazador nest directly south of Jacobstown.
• The Fort - At high player levels one can be found on a legionary blacksmith

Be aware that most of these locations are dangerous for a low level character.