Haven't been kicked by a horse, but I've seen one take out the radiator of a Landrover...

It was a match day (I live near a first division football team ground) and the police horses were out as usual, doing traffic and crowd control. One was calmly walking up the road, keeping traffic at a stop whilst team vehicles turned into the ground ahead. Immediately behind the horse was a landrover, the driver of which was an impatient kind and decided to hoot his horn. The horse took fright and bucked with both rear feet landing directly in the radiator grill. The officer calmly walked it forward, dismounted, looked over the animals' rear hooves, walked up to the land rover driver and chewed him a new one... he charged him with careless driving and damage to police property, then threatened to add obstruction if he didn't get his vehicle off the road in 5 minutes - the radiator at this point was pouring its contents down the road!

LTS