I'll start with two.
a grill delete kit ...
a cup holder delete, center console
those CDC lights that get rid of the lens cover and make it look like the earlier mustangs
Drop in Crate motor that makes 450hp N/A turn key.
cup holder delete is already here. Steeda or someone makes a billet insert with a GT logo that blocks the thing up.
not exactly what I had in mind ........
I was hoping for a new streamlined, custom console unit