This is my son and my JRT, Gunny, playing the Harmonica.  
What silly thing can your pet do??

I know this sounds crazy and I'm not sure if you would call it a trick but listen to this.....  My horse Faye lives in a pasture(most horses do).  As we all know there are prairie dogs (ground squirels) living in our Colorado fields and pastures.  Well, they dig holes an can cause serious injury to a horse or any animal that catches a leg in one of these holes.  So Faye (my horse)  will stand and watch for the prairie dogs to "pop up" out of the holes and will try to stomp them back down. Just like the game whack a mole.   Is this a trick or just a very smart horse!