The scariest thing that has ever happened to my on a bike that didn't involve humans or autos:

I was spinning slowly up a steep section of fire road , a ridge to the right, a hollow to the left, when somethig huge buzzed my head with a terrible loud noise.
It scared the s#*@ out of me. Almost knocked me off of the bike.

A wild turkey had flown from the ridge into the hollow and apparently was trying to impress me. I was impressed. I didn't even know the things could fly like that.