At Alton Towers, I've been stuck on the Air lift hill and brake run for about 5-10 minutes. Both times for phones.
I got stuck on Oblivions lift hill because someone on our car had their phone out.
The best one so far was getting stuck on Thirteen right at the end, we came out of the tunnel section and got stuck where the track switches. They sent out a member of staff who was really fun. I remember him saying something like "does anyone need the toilet?" and a girl put her hand up and he said "I hope you have a strong bladder" to which everyone laughed apart from the girl.
He just made small talk with everyone until the ride was running again. I assume it would be much worse to be stuck on the indoor section.
The worst, and most dangerous situation I have been in on a ride was on one of these
I had been on the ride a million times, but once, when I was about 8 or 9, I went on with someone and the safety bar came fully undone...Now, its not the type of ride you would fly out of, but because I was quite small, I was moving about a lot, and I felt very unsafe at the time. It really shook me up and it took me years to get back on that ride.