... I'll repost my own comment before someone else does again.

My aunt had a service dog named M.D., and he could do all of these things, plus a few. If you showed him an object, he would remember it, and could retrieve it for you. There was a rag on the fridge door, so he could open the fridge and grab food for my aunt, but my uncle, being the joker that he is, decided to teach M.D. how to fetch beer so he didn't have to get up from the couch.

M.D. seemed to grasp the concept, and could recognize the can, but when my uncle put him to the test later that night, M.D. left and never returned. After about 10 minutes, my uncle decided that something must be wrong, and went to check up on him. M.D. had grabbed a beer from the fridge, but his teeth had lightly punctured the can and he had dropped it. Confused, he had tried again, and again, and again. There were punctured cans of beer all over the kitchen floor, and one very distraught dog in the middle of it all.

I think the thing I loved most about that dog is how he would play fetch. My aunt would tell him to sit, then drive her wheelchair a few hundred feet, and drop a tennis ball. When she yelled fetch, he would run over, pick up the ball, and put it in her lap. A game of fetch might last 30 minutes, with only a few "throws," but M.D. never seemed to mind.

He was the smartest dog I ever met. He, and the person who trained him, are heroes in my mind.