I can't answer this with one thing. I love to teach tricks, all tricks. I think they are great because dogs can learn them very young and because they are so much fun, it builds a strong bond with your dog. And the dog learns to enjoy learning! Which one? and Wave are really fun. In Which One, you hide a treat in one fist and the dog uses his paw to tap the hand with the treat. It's a real crowd pleaser. I have a video of that and more tricks on my page at
http://loveyourdog.com/tricks.html
http://loveyourdog.com/tricks.html