A few, some notable ones.
Once when I was a kid at the beach, was in the water and a sudden strong current grabbed my legs and pullled me underwater for a second, brief but unpleasant.
Another time I was on a reserve out in the bush and a group of us were gathering cut grass left by a tractor with a mower on the back. I suddenly hear this crunch and then whistling sound and look around, turns out the mower had run over a fairly big sized stone and sent it flying which almost hit me, which was now rolling down the hill.
I can't imagine either of these having ended very well.