I have a friend who instinctively thumped a suspect in the head with his drawn Glock after the suspect jumped out of the bushes and rushed my friend at close quarters. The slide jumped the rails and made the gun totally inoperable, as in not even a single shot. That was 10-12 years ago, though, and I have no recent reports of such a thing happening with newer model guns.
IIRC the 2nd Gen Glock's failed the Secret Service's "Frisbee" test, where they threw it like a Frisbee onto a concrete surface; the slide popped off nearly every time. That was embarrassing to Glock, so when they made the Gen-3, they fixed that problem.
