The Classic Kong is the staple mental enrichment toy for your dog.

Stuff it with food or treats for your dog to enjoy.  You can also freeze it for prolonged enjoyment!

Mental enrichment is very important for dogs, and can be used to your advantage if your dog has excess energy around the house.  Any mental activities tire a dog out (in a good way), and are fun for your dog to work at.  These types of activities also encourage problem solving which is an important life skill for a dog to have.