Whta is the scariest thing your GSD have done to you?
Phenix really scared us when he was around 6 months old. We were at the dog park. I don't know if I will be able this describe it clearly, but the park is on a small hill.
It's a field owned by the city, so they have built a garage into the hill to store their tools. You can imagine: they digged into the hill, so there is a hole on one side of the hill, but no fence to protect dogs from falling into it.
Phenix was never approching this whole, until one day, when a guy threw a ball in that direction. Our little boy was so focussed on it, he didn't see the edge and felt 8 feets downs into the hole

.
No sounds. No movements. We were freaking out. I ran there and he was sitting there, looking at me, not realizing/understanding what had just happen

. Thankfully, he was all right, not injured. I was so happy!
From there, I wrote a letter to the city to ask them to put a fence around the entry of the garage because it was not only dangerous for dogs, but also for young children. No response. They never did anything to correct the problem.