We show that studying the single top quark production via the W-gluon
fusion process can provide unique information on: (i) the measurement
of the decay width GAMMA(t-->bW+); (ii) probing the symmetry breaking
mechanism by measuring the form factor of t-b-W;(iii) testing the effe
ctive- W approximation prior to supercolliders; (iv) testing CP violat
ion by observing different production rates of ppBAR-->tX and ppBAR-->
tXBAR, (v) testing CP violation from the almost hundred percent longit
udinally polarized top quark decay; in addition to the measurement of
the top quark mass. In contrast to the recent claim by R.K. Ellis and
S. Parke, we show that this process is extremely useful at the Tevatro
n. With appropriate kinematic cuts, we find there are about 10 top or
anti-top events (including the W branching ratio into e or mu) from th
is process produced at the Tevatron with 100 pb-1 luminosity, square-r
oot S = 1.8 TeV and 50% efficiency for tagging a b-quark.