Motivated by recent measurements of the top quark forward-backward asymmetry
at the Tevatron, we study how t-channel new physics can contribute to a large
value. We concentrate on a theory with an abelian gauge boson possessing flavor
changing couplings between up and top quarks, but satisfies flavor physics
constraints. Collider constraints are strong, but can be consistent with the
aid of small flavor diagonal couplings. We find that M_Z' ~ 160 GeV can yield a
total lab-frame asymmetry of ~18% without being in conflict with other
observables. There are implications for future collider searches, including
exotic top quark decays, like-sign top quark production, and detailed
measurements of the top production cross section. An alternate model with a
gauged non-Abelian flavor symmetry would have similar phenomenology, but lacks
the like-sign top signal.Comment: 5 pages, 4 figure