Spiked leather armor is a variation of studded leather armor. Most commonly seen in Fantasy Role-playing games, and in movies like Mad Max.
This armor consists of a soft leather shirt or jacket that has had spikes affixed to it. Not normal punk rock spikes, but 3 to 6 inch long nail-like spikes, capable of inflicting heavy damage on an opponent. This armor is not common equipment because it can be more dangerous to the wearer than it is to his opponent, falling down in spiked leather can be fatal as the wearer is pierced with dozens of his own spikes.
This armor is most commonly seen among gladiators and barbarians. Although hill giants have been known to wear this armor in the various AD&D worlds, their thick skin makes this armor much less dangerous to them than it would be to a human.
Spiked leather usually has to be made specially for each wearer, as the placing of the spikes has to be customized to each wearer's body, to keep them from constantly poking themselves.