A cold/wet weather alternative to tennis balls... I use these or tennis balls with a NERF ball thrower (looks like a blue jai-alai C shaped thrower at $10) in fall or winter. Tennis balls get slimy and wet from moisture or the dogs mouth. If you have a fenced tennis court, fall and winter are excellent for retrieving as a game reward as you get obedience commands. A tennis court is nearly perfect for 'here'  (recall) since the dog cannot run away and learns that 'get it'  and 'out'  of the blaa result in playing the game.  Some dogs quickly learn the fun of retrieving.