Jury Rigging

 is a perk in Fallout: New Vegas and has not appeared in any other of the games in the Fallout series

Effects
"You possess the amazing ability to repair any item using a roughly similar item. Fix a trail carbine with a hunting rifle, a plasma defender with a laser pistol, or even power armor with metal armor. How does it work? Nobody knows…except you."

The perk basically allows you to repair items based on category, instead of type. For example, you can repair the rare Ranger Sequoia with the common .357 magnum revolver. Same goes for armor and clothing as well. Essentially, this perk is very useful by allowing you to use more common items to repair other, more uncommon items.

Many consider the greatest asset of this perk to be the ability to repair and maintain rare and hard to obtain items using simple mundane ones. Ranger Veteran Armor can be repaired using any medium-class armor, and guns that use similar ammunition types can repair each other (such as the Assault Carbine and the Light Machine Gun). However some weapons can be repaired beyond just their own gun and ammo type, hunting rifles for instance, can be used to repair lever-action shotguns and hunting shotguns.

Word of warning though, that once this perk is taken, unique and modded weapons WILL show up on your repair screen just like they did in Fallout 3, since these unique (or modded) items are nonetheless in the same category as their base items. As such, you are advised to be cautious as to what you're trying to repair, with which item as ingredient.

Basically, the game treats weapons into six categories. One handed guns, one handed energy guns, two handed guns, two handed energy guns, melee weapons, and unarmed weapons. Though there are exceptions, you can bet if two guns use the same ammo, you can repair them with each other