I would have to say that my scariest ride was when I was riding alone and was going at a really fast lope and went around the corner of a narrow trail and there was a huge suburban creeping along about fifteen feet in front of me.

I either had the choice to turn into the car or into the tree on the other side. I decided to hit the tree, smashed into with my knee and hand, sprained it pretty good and gashed up two of my fingers. My horse was ok. I was alone too(not smart, I know lol) but luckily my mare is extremly good and I just laid the reins on her neck and she got me home. She cantered for about two or three miles because I was worried I was going to pass out and wanted to get home. She did amazing that day...
Interesting ride was with the same mare and we rode home in a snowstorm along the rode when we got caught in the storm at a friends house. Pitch black out and sleet/snow blowing hard. Shaneequah(my mare) did her extended trot all the way home. My friend that was driving along side us in the van was clocking her at fourteen miles an hour at her trot...
Funniest was when I was riding a Quarter Horse pony cross and he jumped into a dam when the other horses went in front of us. He landed right in the middle with a big splash.