In Kruger National Park, we saw a family of three rhinos (father, mother and baby). They wandered around munching on trees and doing what they do.
Eager to get a closer look, I pulled the rental car within about 20 feet of them. The father did not like us getting that close to them. He turned and rammed the passenger side of the car. His horn went through the sheet metal in the door, but did not come into the cabin compartment. I threw the car in reverse and floored it, driving about 1/8 of a mile in reverse. Got to the top of a hill and just watched the guy for 20 minutes until he cooled down and wandered off.
I've never been so scared in my life to this day. I don't think my passenger (a friend of mine from Hamburg) has forgiven me for it yet either.