I've only been stuck on one ride ever and it was in Busch Gardens Williamsburg on Apollo's Chariot. That ride is wickedly awesome, IMHO.
It was about 95 degrees out in July. Got on and pulled my harness/tbar thing in place. I'm 5'11" and about 165 lbs and these seats and restraints were even tight for me.
I kid you not, this 400 lb PLUS guy gets on and the idiots running the ride proceed to RAM the bar into place trying to squeeze him in. After 2 or 3 tries, they got it to click once, but not enough to release the safeties to send it out of the station.
It was also enough to not allow the system to release the bars on ALL of our seats. So there we are, jammed in our seats. 95 degrees out, about 90% humidity, and we cannot move an inch out of our seats. They tried and tried to get it fixed, but couldn't unlock him or reset the system.
We are now out there about 15-20 minutes in the blazing sun. I'm one of those people who normally barely sweats and it was just pouring off of me. you know that scene from Airplane where he's landing the plane and the sweat is coming off like a garden hose? that was me and most people were 10x worse off.
A manager and supervisor came over and basically flipped out. The only way to reset the system was to apparently get the huge guy's restraint clicked further to hit the electrical contacts to trip the safeties or whatever. They had like 5 people pushing on this bar trying to get it to go in further so it would click. I though they would kill this huge fat guy. At the time, I didn't really care since I thought I was about to get heat stroke.
They finally got it to click and could release the safeties. The manager fired at least two of them on the spot from what I could hear and they shut down the ride. I could literally wring the sweat out of my shirt at that point. It was awful and some of the people had to sit down on the platform and wait for EMS. Now THAT is a thrill ride!