Well, definitely not the Carousel of Progress. I was stuck in the last scene for about 3 or 4 rounds and I was about to go crazy. That place has no escape.
Getting stuck on rides isn't cool for me just because of the repetition factor.
One time, we got stuck on Carousel of Progress; I think somebody went out during the show, because, it had to go all the way through the program to reset, without the stage moving. It was interesting, and kind of scary at the same time, because we were in the first scene, and it appeared it was totally broken.
Then, once we were stuck on the Mexico ride at Epcot for so long we were late for our reservation at Biergarten, probably about 30 minutes or so. It was when it was newly renovated, and we were stuck at the Market scene part. All the lights were turned on, but, they didn't evacuate the ride. It was nerve wracking, but not scary, because of the reservation.
But, by far the worst was the time we were stuck waiting for Philharmagic. It was about 10 years ago, we were with my brother and his family, with 3 children less than 5 years old, and they held us in the waiting area just outside the auditorium for nearly an hour, before deciding that they needed to shut the show down. My two year old nephew was so bored that he broke his "opera glasses". That was one of the worst experiences at WDW. They gave us a fast pass that was good any time, that I don't think we used on that trip.
The closest thing to an actual "evacuation" was one time with the train to Rafiki's planet watch. Instead of the train, we were put on buses, and had to walk an alternative path to get to and from the planet watch. Mildly interesting to see a different part of the park.