I never stopped pushing for a Ferrari :-)) but usually ended up with the quart of wine which as it turns out, from my experience anyway, to be the classic gift for an instructor.
Of all the students I ever had, and all the gifts they gave me, wine was definately the most offered and the most appreciated. It doesn't kill the student financially, says "thank you" in a nice way, and is considered the world over as a classic gift for such occasions.
Dudley Henriques