The Everlasting Fun Ball

This little guy is worth it's weight in gold! I use it in training about as much as I use a Kong. The big difference is that with a Kong you can stimulate your dog to lay down and chew, which has it's own advantages, but with the ball, you can stimulate your dog to chase, run, jump and fetch. This is a very effective tool for the flexibility you get out of it. It works as a reward when stuffed with treats, as a ball for play when empty and as a training tool when used to lure or bribe.

The cost is minimal for all that functionality. Smalls will run you around $5 and the large around $12. It depends vastly where you buy from. Here in San Francisco, all the boutique shops will be higher then buying online and the mega-stores (Petco, Pet Food Express) have slightly better pricing but I've noticed them running out of stock.