Lol I've had some interesting experiences with mountain biking...
I was on this trail I had never been on, and it wound thru this field and ended up at the edge of a gully. So I started to go down the gully (it went down then up again) and for some stupid reason I pulled my front brake first... I've got the brakes really tight on my bike so you hardly have to touch the lever and it will fully stop your motion. Well, bad luck considering I was on probably at least a 7% grade, (facing downhill) and I had just *stopped* the bike using the front brake. Well, it doesn't really stop you from being thrown forward off your seat, so to avoid going ~15 ft down a rocky hill I had to throw all my weight towards the right. I stopped moving but I had another lucky surprise of getting the headset of the bike thrown at my face. (In case you don't know much about bikes the headset is the handlebars, anything attached to them like brake levers, shift levers, etc, and the post that attaches this to the rest of the bike.)
Usually stuff with my bike isn't as crazy, but I do manage ways where I can wreck parts if I'm not careful. Not major things if taken care of right away.
For example I was on another trail (yes I do quite a bit of mountain biking) and got a stick stuck in my derailleur (the part that moves the chain from sprocket to sprocket on the bike). Doing that kind of stuff will wreck the derailleur, which makes it hard or impossible to switch gears...
Luckily my cousin who was with me noticed it and I got it out before much harm happened...
I guess that's enough of my stories...