Drag 'em Down (3.5e Feat)
From D&D Wiki
Drag 'em Down [Racial, Fighter]
You know how to bring your opponent to the ground
Benefit: A character with this feat that hits with a bite attack or unarmed strike can attempt to trip the opponent as a free action without making a touch attack or provoking an attack of opportunity. If the attempt fails, the opponent cannot react to trip the character.
Normal: See Trip.