Had a dump truck fixing to T bone me at an intersection. No way out going forward, shifted into reverse going about 20 MPH in drive. Got out of the way of the dump truck, but most of my tranny was laying in the pan, two or three good handfulls of small pieces and metal chips.
Have on a very few occasions, when I´m fixing to tobogan down an ice covered slope, used reverse as a last resort. Really messes with the steering or whatever steering you had before shifting into reverse. After a few trials, I gave up the technique. Most any other technique was more productive. I´ve sometimes used this technique when driving tracked vehicles, doesn´t work nearly as well with wheels.
Have on a few occasions, while doing a tranny pressure test, shifted from drive to reverse (at very low speeds) with all the wheels off of the ground. Which would sometimes peg the pressure gauge, which can´t be a good thing.