The nosewheel does the real turning, either via the rudder pedals (limited throw) or the tiller (much more authority). However, the rudder is connected directly to the pedals, so it will move on the ground as well, whenever the pedals are used.
The tiller overrides the pedals for the nosewheel, but the pedals control the rudder.
I don't know about the 777, JWL, but yes, we do use the rudder pedals on a 737 while taxying as Intruder has described, if the change in direction required is limited - as in running along a straight taxyway, but the amount of nosewheel movement achieved is small. Bigger turns need the 'tiller'
Location: last week I was in....now, where am I now?
and using the rudder to keep the aircraft on the centerline is smoother than with the tiller. This makes life for the cabin crew also easier while demonstrating the essential life saving procedures to the newspaper reading audience.
Some confusion has been introduced. Taxiing while using the rudder pedals isn't using the rudder to taxi. The limited nosewheel steering authority is available through the rudder pedals during taxi. Much more steering authority is available through the tiller.
When one taxi's and uses the rudder pedals to maintain the taxiway centerline (taxi straight), one isn't using the rudder to taxi. One is using the nosewheel steering. While the rudder pedals do move the rudder, the effect of the rudder is negligible (read worthless) during taxi. It's the limited nosewheel steering through the rudder pedals that's being used.
To answer the original question, the rudder isn't used to taxi. Sometimes the rudder pedals are. The primary taxi control is the tiller, which directly controls the movement of the nosewheel steering.
Brakes may be used for some taxi operations in a limited way, in some airplanes. Some aircraft such as the B747 also use body gear steering, in which some of the main landing gear also turns, but turns in the opposite direction as the nosegear, to effect steering. This isn't controlled by the pilot, but is part of the nosegear steering system, and takes effect when the nosewheel has moved through a certain amount of travel (20 degrees, for example).