Some of you might get a kick out of this story. 

Some years ago when I was flying the 757 out of KJFK, we had just pushed back out of the gate into the alley to start out trip to KSFO.  As the tractor pulled us to the middle of the taxiway the ground tug driver called and said "park the brakes."  I radioed back "brakes parked, further signals by hand."  This meant that when the tug and tow bar were removed, the driver would pull the tug to the side out of the way and get out of the tug and give us hand signals which would be a salute from the driver and also be me flashing a landing light to confirm. 

As the tug began pulling away we called Kennedy ground for taxi clearance.  As soon as I started moving the 757 it was evident I had no nose wheel steering.  Since the tug driver did not have a radio it would be impossible to contact him to get him back and fix the problem which was very simple - he needed to turn a valve, which he had turned that shut off hydraulic pressure to the nose wheel steering, so he could steer the plane during push-back.  The valve needed to be re-opened again so I could steer the plane with the nose wheel tiller.  Both the co-pilot and I tried to get his attention by opening the cockpit window and yelling, but the noise was too loud for him to hear us. 

Then a light bulb went off in my head!

I lifted the engine thrust reverse lever on his side of the plane to idle reverse and put it back to forward thrust.  That got his attention and we waved him to come back.  He returned to us and plugged into the intercom and asked what was the problem.  When I told him I had no nose wheel steering you could hear the embarrassment in his voice.  A simple twist of the valve, and we were on our way.