For whatever reason, whenever I ride HM at MK, I get stuck in the graveyard scene, on the hill going backwards. Most of the time the music keeps playing, although there was one time where we were stuck for a good 5-7 minutes and the music totally stopped, which is a whole other level of creepy in that room.
Also got stuck on RnRC, just before the coaster takes off in the tunnel. We sat there for a good 10 minutes, and when we finally took off, there was no music. As we approached the exit, we were all loudly complaining about the music - can you imagine 9 teenage girls all screaming "THERE WAS NO MUSIC!" The poor CM letting us off looked so frightened he literally opened a door on the side of the room and let us cut the whole line.
DB and I were stuck on Space Mtn at DL once, just as we were about to approach the loading dock. After a few minutes of us not moving, but the rocket ahead of us going through the ride sans-people, they started to clear out the queue, and we could see the lights inside the building turn on behind us. And then every cast member LEFT; they literally all walked out! We were alone, stuck in the rocket, for a good 10 minutes. Long enough for the 5 or 6 pre-teens in front of us to sing "Under the Sea", "Be Our Guest" and something else, screaming at the top of their lungs.

Finally a CM returned and they let us off using a stepladder.