  Modified Gauss-Bonnet, i.e, $f(G)$ gravity is a possible explanation of dark
energy. Late time cosmology for the $f(G)$ gravity non-minimally coupled with a
free massless scalar field have been investigated in Ref. [32]. In this paper
we generalize the work of Ref. [32] by including scalar potential in the matter
Lagrangian which is non-minimally coupled with modified Gauss-Bonnet gravity.
Also we obtain the conditions for having a much more amazing problem than the
acceleration of the universe, i.e: crossing of $\omega=-1$, in $f(G)$
non-minimally coupled with tachyonic Lagrangian.
