This is the greatest glitch , thus far.......
1. Go to a shop keeper in any city and trade with them
2. Look at the vendor's inventory and make sure they have at least 2 of the same item. Alternatively , you can sell the vendor one item from your inventory that they already have in stock.
3. Buy the cheaper of the 2 items and sell it right back (nothing happens the first time usually by the second or third try the glitch happens), you will lose a little money but don't worry you'll get it back.
4. After the second or third try , you will notice that the item you have purchased and sold back is now full repaired!!! Meaning you can sell it for a very nice profit. Once you sell it , you will also notice that the item is back to its original condition in the vendor's inventory (also at the original price). However , if you buy it back at the low price , it will once again appear fully repaired in your inventory!! This is a wonderful way to buy everything in the shops in every city for FREE.
5. To repeat , wait for 4 days for the shop's inventory to replenish and do the glitch all over again for infinite ammo , caps , meds , chems ....everything!!
6. Repeat as many times as you desire....
NOTE :
This is also a great way to get good , fully repaired , armor and weapons. Instead of selling the weapon or armor , simply keep it (after emptying out the shop of course) and use it in combat.
If you have 100 repair , and you have several versions of the same customized weapon , this is a good way to fully repair it without losing the second version (as you would while repairing it yourself) , however if you have less than 100 repair , using this glitch will get it repaired as high as your current repair level.
With this glitch there is no more worries of running out of precious .44 or .308 ammo , or any other ammo you give to your followers , simply wait for the shops to replenish their inventory and rob them blind using this glitch , to keep your followers ammo stash high.
I tried this with the following : Hunting Rifle, 32 Pistol, Scoped Magnum, 10mm SMG, Laser Pistol, Laser Rifle, Baseball Bat, Brass Knuckles, Chinese Assault Rifle, Chinese Officer Sword, Chinese Pistol, Combat Knife, Combat Shotgun, Sledgehammer, Lead Pipe, Minigun, Missile Launcher, Police Baton, Pool Cue, Power Fist, BB Gun, Sawed-Off Shotgun, Sniper Rifle, Switchblade, Knife, All common clothing, All common armor, All common helmets. The glitch worked every single time.
You can also do the same with outcast/enclave/brotherhood power armor/helmet that you find in the wastes , just make sure you have at least two of the same , sell them both , buy back the cheapest one , after a few tries you have a fully repaired power armor/helmet. The same can be done with raider gear , talon armor , regulator dusters anything , basically , that you have two of.
Enjoy .....