Stunning Fist

Type of Feat: General

Prerequisite: Dex 13, Wis 13, Base Attack Bonus +8, Improved Unarmed Strike

Required for: Extra Stunning Attacks

Specifics: The character can attempt a disabling strike with a -4 attack penalty and a -4 damage penalty. If successful, the target must succeed at a Fortitude save (DC 10 + 1/2 the attacker’s level + the attacker’s Wisdom modifier) or be held for one round. This attack may be used 1x/day for every four levels of the character.

Use: Selected

Monks suffer no attack or damage penalties when using this feat and may use it 1x/day per level. Constructs and Undead are immune to this attack, as are any creatures that are immune to critical hits.

This is an effective way of dealing with stronger or more dexterous opponents, as they'll be unable to fight back for a brief time.
Beamdog has nerfed this ability to have a duration of 1 round.

Jan 11, 2017:

• Cannot be attempted on players already stunned by a previous Stunning Fist attack.