My Tibbe is almost 8 years old and the only time he really wags his tail is when he's playbiting ME!!!
He dog laughs, squints up his eyes, jumps up and down, goes around in wild circles and bounces around otherwise to show he's happy but I really only see a cute little wagging tail when he is besting me in hand-fighting and gnawing down on me - then his stubby little tail wagging like mad! He's the only dog I've ever had who doesn't wag his tail when happy.