Significant breaks for me:
when a young fella my mum was fiddling with my Swoop while talking on the phone, I might have been getting her help transforming it, either way, she snapped off the upper or lower jaw, and it's never been the same. She did feel horrible.
when even younger, my baby sister sat on my g1 prime trailer (it was about the right size for her to use as a chair) and the hing holding the back door on failed. the door will sit there closed but falls off readily.
My G1 mirage has one of the spoiler tabs broken off, the spoiler has been held in place with some blu-tac for over 20 years. probably nearly 30.
binaltech wheeljack has a damaged spoiler, I plan to glue it back together at some point.
I have been supremely lucky over the years.