@crashgate, because it is a low poly model, do not be afraid of triangles, they are your best friend in low poly, it isn't like mesh smoothing where it makes divits, everthing in low poly is made out of a triangle except you don't control them unless you want to, the computer controls it otherwise.
There are lots of places you can get rid of those weird rectangles and replace them with triangles to get a smoother finish.