Shock Wave( Draconomicon, p. 73)
You can strike the ground with your tail so hard it knocks other creatures down.
Power Attack (PH) , STR 13, dragon, size Large or larger,
You may, as a full-round action, strike a solid surface with your tail and create a shock wave that radiates out from your space and continues for a number of feet equal to 5 Ã— your racial Hit Dice. Make a bull rush attack by rolling once regardless of how many creatures are in the radius. Every creature in the radius makes a Strength check and compares it to your roll. Those who fail their opposed checks are knocked down.
Structures and unattended objects at least partially within the shock wave take damage equal to 1d6 + your Strength bonus.