When a hollow, elastic ball has been partially filled with a fluid, the rebound after being dropped is suppressed quite substantially. This principle helps a roller hockey ball to remain on the ground rather than bounce during play. Future research may lead to other other applications such as passive damping systems based on sloshing liquids.
In the video below, two Skyballs are falling from the same height, the one on the left is empty while the one on the right is partially filled. Notice that they have nearly the same rebound on the first bounce, however, after the second rebound the fluid motion mitigates a significant portion of the bounce.