I had to call for a ride due to mechanicals a few times. My freehub froze in the disengaged state while commuting at -18C at pretty much the mid-point. Broke the RD off my fat bike riding in thick wet clay. Clay packed the chain then as it began to dry the chain became stiff, leading to chain suck. I learned that day that one thing you shouldn't do when you experience chain suck is try to "power through it" by pedaling harder.
As a teen my quill stem clamp broke off while I was riding. Managed to come to a stop with disconnected handlebars without crashing, then walked home.