in 3 years of playing this is the first time it's come up.
a bad guy runs past the crossbow wielding wizard provoking an AoO. however the crossbow is empty so the wizard tries to punch the bad guy. the wizard (oddly enough) doesn't have improved unarmed combat and provokes an AoO for attacking unarmed. so can you provoke an attack of opportunity while acting on an attack of opportunity?
also if the wizard had a wand in his hand could he use the wand to cast a spell in reaction to the AoO?
a bad guy runs past the crossbow wielding wizard provoking an AoO. however the crossbow is empty so the wizard tries to punch the bad guy. the wizard (oddly enough) doesn't have improved unarmed combat and provokes an AoO for attacking unarmed. so can you provoke an attack of opportunity while acting on an attack of opportunity?
also if the wizard had a wand in his hand could he use the wand to cast a spell in reaction to the AoO?