A friend of mine got kickback on a board he was cutting on his tablesaw. He was in the right position and using a pushblock and so had no injury, just a bewildered 'What was that?'
What that was, was represented behind him. He has an interior door behind him and his saw, and his workpiece very nicely impaled it, and nearly went through it.
He thought about it, and trimmed (shortened) the piece, but left it in the door as a reminder...
His wife finally talked him into taking it out, but it was several months.