I think the P-40 has a real mystique thing going. It was there at the beginning of the War and proved to be a rugged and versatile combat plane. A number of nations used the Warhawk in many different theaters, so there were naturally alot of different paint schemes.
It immortalized the shark mouth, too. A few other planes sported them but it just doesn't look at home as on a P-40.
Long live the Tomahawk, Kittyhawk, Warhawk!