  The recent forward-backward asymmetry recorded by the CDF Collaboration for
the top and anti-top quark pair production indicates more than $2\sigma$
deviation from the Standard Model prediction, while its total production cross
section remains consistent. We propose a $W'$ boson that couples to down and
top quarks. We identify the parameter space that can give rise a large enough
forward-backward asymmetry without producing too many top and anti-top quark
pairs. Other models presented erstwhile in the literature that can produce such
effects are also discussed.
