Are PCs automatically proficient with unarmed strike? (I.e., without taking Weapon Proficiency: Simple.) For example, if a 3rd level Wizard attacked a 1st level Commoner with an unarmed strike, does he take the -4 non-proficiency penalty?
i'm pretty sure everyone/everything is considered to be proficient with their "natural attack form". unarmed strikes would be the natural attack form of most humanoids.
When humans attack unarmed with out the Improved Unarmed Strike, they suffer an Attack of Oppertunity for this attack. But there are no further penalties...
It should be pointed out that the wizard would only suffer an AoO if he attacked an armed commoner. You suffer the AoO when an unarmed person (without Improved Unarmed Attack) attacks an armed one. If one unarmed person attacks another unarmed person (without Improved Unarmed Attack) there are no AoO's exchanged.
Just thought I'd point it out, since my group didn't know this at first, and a very silly fist-fight occurred before we cleared the matter up.