Another one I thought of while listnening to the Pulp Fiction soundtrack is “If Love Is A Red Dress (Hang Me In Rags)” by Maria McKee.
The main theme from “Peter and the Wolf” is my personal favorite.
I came into this thread specifically to mention that tune. It can be maddening, though, as it’s very hard to stop whistling once you start.
I’m also prone to whistling portions of The Barber of Seville and The Marriage of Figaro. Specifically, those portions used in “The Rabbit of Seville”. 
Sweet Georgia Brown! (better known as the Harlem Globetrotters theme song)