The Spiked Knuckles can be acquired very early in the game - the Dunton Brothers each have a set to steal, and wield a second set in combat. If the player chooses to kill them, they can acquire four sets of Spiked Knuckles.
Spiked Knuckles are commonly found on low-level Raiders, but can also be found randomly in compartments and merchants. They seem to be almost as common as the weaker Brass Knuckles.You can find several in the Lockers in the Elementary school
For a character with one or more ranks of the Iron Fist perk, the Spiked Knuckles serve as a very effective low-level weapon. Even with a very low unarmed skill, three ranks of this perk and the Spiked Knuckles can deal a heavy amount of damage. Even after acquiring the Deathclaw Gauntlet or one of the Power Fist variations, the Spiked Knuckles could be used against low-level enemies in order to preserve the durability of more powerful weapons.
Even if a player isn't focused on unarmed in combat, carrying a set of Spiked Knuckles is a good idea to save ammo or if you just feel like beating your enemy to death with your hands. It's low weight and damage boost over bare fist makes this a must have inventory item.