Once saw someone drop a can of paint on the platform of a Routemaster bus in London. Boy did it make a mess.
On a more serious note, I was following an estate car on my motor bike one night, when the car lost control and hit a tree. The car was being used by a Painter and had ladders and tins of paint in the back. The paint cans shot forward, hit the back of the front seats and exploded filling the car with paint. The driver staggered out covered from head to foot in gloss paint with it in his eyes and everywhere. I got him to the side of the road and sat him down till the ambulance arrived, but he was in quite a bad way with the paint stinging his eyes, and I ended up with quite a bit of paint on my clothes as well.