Merchant

Aside from dead enemies Merchants are the primary source of items and equipment in the world of Fallout. Merchants operate out of either fixed stores or traveling caravans.

Fallout and Fallout 2
Most NPCs can be bartered with. In addition, almost all friendly towns have 1 or more merchants with a substantial and replenishing selection of items for sale and a large amount of caps. The general store is the most basic shop and can be found in most settlements. Doctors sell medical supplies and are also present in most towns. Weapons and Armor merchants can be found in larger settlements such as the Hub and San Francisco. In both Fallout 1 and 2, the further south they are the better stocked they tend to be. The Gun Runners have the most advanced weapons in Fallout 1 while the stores in San Francisco have the most extensive inventory in Fallout 2. Shops specializing in other wares can be found.

Traveling merchants can be found traveling the wastes in guarded caravans. They usually sell assorted merchandise but can occasionally offer a unique item.

Shops and Merchants in Fallout 1
Vault 13 Medic, Razlo, Darkwater's, Gizmo's, Doc Morbid, Hub General Store, Library, Iguana Bob's, Beth's Gun Store, Maltese Falcon, Old Town Arms Dealer, Vance (drug dealer), Thorndyke (healer), Water Merchant Vendor, Brotherhood Doctor, Tine's General Store, The Gun Runners, Cathedral Gift Shop, Dr. Wu

Fallout 3
In addition to General stores and Medical Doctors most towns also have a food vendor/bartender as well as one person who can repair items. Clothes shops can be found in richer settlements. Weapons/Armor shops are found in Rivet City, The Citadel, and Paradise Falls. Rivet City also has a dedicated Chem dealer.

There are four caravans traveling the DC Wastes. One dedicated to food/chems, another to weapons, another to armor, and the last to junk items. They can be invested in to improve their selection and repair skills but they are vulnerable to attack. In addition to the caravans, Wastelanders can be found who will sell random items or sometimes rare items. Some special encounters with doctors, chem vendors, and hunters (food vendors) are also possible. Inventories will scale by level but certain advanced items like advanced power armor and plasma weapons remain unavailable. Price, aside from discounts appear to be constant across stores.

Merchants have a new inventory after a period of three days, and then again after a period of four days, in order to correspond with the length of a week. The inventories update at 12:00 AM the day of, although which days these updates occur vary from player to player.