As the final, summarizing example for style topics (HtM, Ch. 8), specifically for theme, leitmotive, and thematic association, I used these four sequences from Casablanca: Rick and Ilsa meet again -- DVD ch. 13; after hours (first night) -- DVD ch. 15; after hours (second night) -- DVD ch. 29; and the ending -- DVD ch. 34. The first three all make use of the signature stinger chord (in fact, these are the only three places it occurs in the film), and the second and third have some close relationships of other musical material (to the point that the third can virtually be considered a "variation" of the second). Students have no difficulty with the leitmotive (the opening of the chorus for "As Time Goes By"), given the way it is first introduced (in ch. 13), and the treatments of the theme in the four sequences offer opportunity for discussion of reinterpreted contexts.
Obviously, many other examples might work as well, but this was relatively compact (useful for a compressed summer semester course) yet gave a good sense of musical strategies in the film as a whole.