Defensive Power
Unexpected Strike (Ex): The stalwart defender can make an attack of opportunity against a foe that moves into any square threatened by the stalwart defender, regardless of whether or not that movement would normally provoke an attack of opportunity. This power can only be used once per stance. A stalwart defender must be at least 16th level before selecting this power.
Rage Power
Unexpected Strike (Ex): You can make an attack of opportunity against a foe that moves into any square threatened by you, regardless of whether that movement would normally provoke an attack of opportunity. You can use this ability only when there are no other foes in a square threatened by the barbarian. You must be at least 8th level to select this rage power.
Vigilante Talent
Unexpected Strike (Ex): You gain Quick Draw as a bonus feat. At 8th level, you can draw hidden weapons as a swift action (instead of a move action).