The one day I spaced a helmet... my horse bolted when some deer ambled by along the hill. I got him under control (I am a very stern mother...) and then proceeded to talk to the deer. They actually came up close to the arena and both my horse and the deer sighed a huge breath.
I don't know which was more scared, but all I can say is I was pissed and kept on riding and went off to put a helmet on.
I would go Jackie Chan on a deer if it ambushed us like that!