In my opinion that piece of flint you have is an artifact, those straight edges with the small scalloped areas are the result of either someone using percussion chipping or punch chipping. They are to even and too similar to be natural. It almost looks like an arrowhead which was being knapped and then messed up by having one punch go clear across the surface and making it too thin in the center to be used.
Of course, you know the saying about opinions right? Everyone has them, and sometimes they stink

Might just be a strange rock too :P