If you have a self gravitating sphere than all *force* vectors point to the centre and are normal to the surface (and other equipotentials). But that means the *gravity* vector does not always point to the centre, since the centrifugal force at any point is not in general directed away from the centre.

The gravitational potential outside of a spheroid if mass $M$ can be expressed to high accuracy with
$$\Phi = -\frac{GM}{r} + \frac{kG}{2r^3}(3\cos^2\theta -1),$$
where $r$ and $\theta$ are the usual spherical coordinates and $k$ is a constant equal to the difference in the moments of inertia about axes parallel and perpendicular to the rotation axis (the object must be rotating to be a self gravitating spheroid).

Taking the gradient of this potential you see there is a term in $\hat{r}$, but also a $\hat{\theta}$ component 
$$g_{\theta} = \frac{3kG}{r^4}\sin \theta\cos\theta$$
that is *not* directed towards the centre of the spheroid.

In the limit of an almost disk-like spheroid, then at large distances from the centre and close to the disk plane, this term will dominate and the gravity will act towards the disk midplane rather than towards the centre of the disk.