How have you modified your gas grill?

Have you converted your gas grill to use lava rock, ceramic briquettes or some other heat medium? There are people who say that without something to hold heat and burn off the drippings, that a gas grill can't produce flavorful food. Since gas grills are not made with lava rocks these days, many people have taken to modifying their grills to get this feature back. How have you modified your gas grill?

Tell us How have you modified your gas grill?