Great topic.
One I thought of immediately, and another that Pond Digger reminded me of...
The first one involved going about 100 feet down a slope to expose a sewer lateral and trench up the hill to the house. There was more slope below the sewer main, with a retention pond at the bottom. My plan was to lock the brakes, lower the front bucket and stabilizers, and essentially drag myself down the hill, then use first gear to add some thrust, and the hoe, to push myself back up as I dug.
(These days I'd say use an excavator, only an idiot would try to take a backhoe down there, and I'd be right.)
Anyway, going down worked out fine. I exposed the end of the lateral, and started my way back up. I'd dug enough for a couple lengths of pipe, and began to push forward again, but I put in a little too much down pressure, and lifted the rear tires, or more particularly, the left rear tire, a few inches off the ground. That meant that the right rear tire was free to roll downhill, even though I was in forward gear. The bucket slipped, the whole machine started downhill, and only stopped when both left side tires, rear
and front, were in the trench, allowing the left stabilizer and front bucket to make contact with the ground once again. The bucket smashed the heck out of the end of the lateral, so once I got straightened out I had to chase even further downhill to fix that problem.
We had a 955 hilift on the job, and used it, and enough chain to reach me and that's how I got back up the hill and finished the job.
(Hey, you asked for scary moments, not intelligent ones.) :cool2
The other one was taking that same backhoe up onto a tilt deck trailer. The deck was a little wet, and the brakes on the hoe weren't quite right. After taking a couple of tries, and not making it on, I thought I'd try second gear and a little momentum. The front end bounced up so I was teetering on the rear wheels, but starting to spin them anyway. I knew if I stepped on the brakes, one of them would grab, and the other wouldn't, and I'd be turned sideways in a heartbeat, so I did the only thing that I could, which was to throw her into reverse, and go backwards, in a big hurry, but fortunately in a straight line. It was a pretty un-graceful landing anyway.
One of the carpenters saw the whole episode. He stopped by the porta-potty, walked on over, and offered me a big handful of TP. (Didn't really need it, but it was close...)