Armor spikes do not have an effective reach. They may not be used as a weapon attack or for Attacks of Opportunity. However, they can be used to inflict lethal damage during a grapple or during a charge attack (ie a shoulder rush).
Gauntlets and Cestus
Characters wearing gauntlets or cestus are -2 on checks that require agility using the hands. For example, climbing, open locks, disable device, catching a thrown object, etc.
A buckler can be used to shield bash for 1d1/1d2 damage. A spiked buckler does 1d2/1d3 damage.