I don't have my PH here, but I don't recall anything clearer than what's in the SRD ...
So far, so good. But then:
Does it matter whether the character is Small or Medium? If not, does the spiked shield still count as a light weapon? And if so, isn't this the ultimate off-hand weapon for a Small Ranger or other two-weapon fighter?
Shield Bash Attacks: An opponent can be bashed with a shield, using it as an off-hand weapon. A Medium-size character deals 1d4 points of damage (X2 crit) with a large shield or 1d3 (X2 crit) with a small one. (The tower shield cannot be used to perform the bash action.) A Small character deals 1d3 points of damage (X2 crit) with a large shield or 1d2 (X2 crit) with a small one. Used this way, the shield is a martial bludgeoning weapon. For purposes of attack penalties, treat a shield as a light weapon. If the shield is used as a weapon, lose its AC bonus until the character's next action (usually until the next round).
So far, so good. But then:
Shield Spikes: These spikes turn a shield into a martial piercing weapon that deals 1d6 points of damage (X2 crit) no matter whether the shield is small or large. Buckler or tower shields cannot have shield spikes.
