Prefab bullet affected by gravity when it shouldnt?

I have a sphere that I can shoot from my character. I have turned off Drag, Angular Drag, Use Gravity, and have set the mass to 1e-07 (Well I tried 0, but thats what the GUI set it to).

Now when I ‘fire’ the sphere at the target, it moves towards the target, but if the target is some distance away, the path of the projectile decays as though gravity was still affecting it. Ideally I want the sphere to travel in a straight line until its destroy timer kills it (So it moves over the target marker and continues)

So what else do I need to set or tweak?

One thought was that my target is currently at a different height to the firing point, so I am wondering if it is the transform that is inducing an arc, but I dont know the math / functions to stop this happening.

http://unity3d.com/support/documentation/Components/class-Rigidbody

Enable isKinematic. Will not be affected by gravity.