Freezing the Lifeblood

Improved Unarmed Strike (PH) , Stunning Fist (PH) (or monk's stunning attack) , Base attack bonus +5, WIS 17,

Against a humanoid opponent, you can make an unarmed attack that deals no damage, but has a chance of paralyzing your target. If your attack is successful, your target must attempt a Fortitude saving throw (DC 10 + 1/2 your level + your Wisdom modifier). If the target fails this saving throw, he is paralyzed for 1d4+1 rounds. A paralyzed character stands rigid and helpless, unable to move or act physically. He has effective Strength and Dexterity scores of 0 but may take purely mental actions.

Using this feat uses up one of your stunning attacks for the day (either a monk stunning attack or a use of the Stunning Fist feat).

You can paralyze a humanoid opponent with an unarmed attack.