In reply to Gordon Stainforth:
I know. My examples were about this. Just a few notes of Apache or Van der Valk, and it's instant recognition. Also various John Williams film scores, of which two examples are already listed. Special mention to his "Hedwig's Theme" from the Harry Potter films, as the leitmotif aspect there has been extremely handy for merchandising adverts, rather like the McDonald's "I'm Loving It" (does that count? It was WRITTEN as a leitmotif, like Brian Eno's old Windows sounds, and that old Nokia ringtone....)