Some dogs fetch tennis balls. Some dogs swim. Some dogs go apeshit over basketball-sized orange spheres. The Varsity Ball ($40) is an insanely durable toy (it's made of FDA-approved linear low-density polyethylene plastic) that's designed to stimulate your larger dog's natural herding instinct and play drive. As the Varsity Pets website notes, it's too big for dogs to destroy or grab onto with their mouths. Instead, they push it around, kick it, and otherwise work themselves to exhaustion as they try to "figure it out." If you have a pet lion or tiger, they seem to like Varsity Balls too.
Image: Varsity Pets, LLC