A guide or escort, especially one who rides in advance.
A forerunner.
One who rides out on horseback to inspect a ranch etc.
One who paces.
A mechanical pencil.
In harness racing, a horse with a gait in which the front and back legs on one side take a step together alternating with the legs on the other side; as opposed to a trotter.
A pacemaker (one who sets the pace in a race).