You can stamp the ground to crush and disrupt opponents.
Prerequisites: Huge size, must have feet, Trample.
Benefit: You may, as a full-round action, strike a solid surface with one of your limbs and create a shock wave that radiates out from your position and continues for a number of feet equal to 5 × your base creatures Hit Dice. Make a single unarmed attack roll. Every creature in the affected area compares its Balance check result to your attack roll result. Those who fail this opposed check are knocked down.
Special: Each structure and unattended object that is at least partially within the shock wave takes damage equal to 1d6 + your Strength bonus + the object's hardness (maximum 5).
Source: Savage Species, page 39.