There are many. I dont think there is just a circle emblem but there are more than one circles (audi) then the is the circle with the triangle (Mercedes Benz), then there is a circle with an L (Lexus). T (Toyota). You have to be a bit more specific.
That would be Dodge, and the emblem is a Ram (goat).
It could be an old Buick emblem.
Ford
Toyota
It is not illegal to put a different emblem on your car as long as it does not misrepresent the make or model of the vehicle.
It is the emblem of a Ford Torino.
A Maserati
maserati
suzuki
Triumph
From the look of the emblem and the large grille, it looks like a Mazda concept car.