When you need to positively make sure you've tired out your dog, make no exceptions then the The K-9 Kannon. Chambered in standard smoothbore tennis balls so no need for expensive custom ammo. Quick reload ball holders built in the gun ensure that no matter how quick they back to you your reloaded and ready to first off again.
Advance your walk time out of the throwing 'stone age' and get the K-9 Kannon modernising your play time arsenal.