Umm, never. That would have to be pretty damn impressive muscle power...

We've broken a couple of toys. I twisted the intensity knob too far on a vibrator and stripped the threads. It didn't work after that. I think that was a case of getting what I paid for: it was a cheap vibe.

When my wife and I were new to pegging, we broke the base off a cyberskin dildo (the european cock with balls) before insertion. That happened because the manufacturer marketed it as "harness compatible" and recommended using the base to attach to an o-ring harness. But when we did, the base separated from the dildo and "plop!" Talk about a mood-breaker!