3e SRD:Armor Spikes
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Spikes can be added to armor. They deal 1d6 points of piercing damage (X2 crit) with a successful grapple attack. The spikes count as a martial weapon. If a character is not proficient with them, the character suffers a -4 penalty on grapple checks when trying to use them. A regular melee attack (or off-hand attack) can be made with the spikes, and they count as a light weapon in this case.
An enhancement bonus on a suit of armor does not improve the spikes' effectiveness, but the spikes can be made into magic weapons in their own right.