My personal favorite is the bathroom music. At my school, there's a speaker in the bathroom. It's motion-activated so when someone walks in, it starts playing a selection of classical music. I have no idea where it gets the music (radio? endless tape loop in the main office?), but it's always something classical.
Occasionally this has a very strange effect on me. My years of playing in various symphony orchestras have gifted me with an intimate familiarity of a significant number of popular classical pieces. So when I go to the bathroom and a piece of music comes on that I've played, it immediately triggers memories that I generally haven't accessed in years. All of a sudden, I'm not standing in the girls' bathroom of a Korean elementary school. I'm practicing the tricky rhythms of "Hoedown" from Rodeo by Aaron Copland with my high school symphony, blasting through Beethoven's 5th during my apprenticeship with my hometown professional symphony, or agonizing over my tiny solo in Dvorak's New World Symphony with the community orchestra I played with in Boston. The effect is immediate and sometimes leaves me shocked that I can even remember those days.
So far, I haven't recognized any of the music I've heard in the ladies' room today, but it's only 9:30am. The day is young and ripe for a flashback.