Ok, gross but true
First, one of my favorite rides was out past a state prison. It is in a rural area, nice shoulders, rolling area - lots of buffer area between the road the prison buildings.
I saw a large pumper truck pull out onto the road, leaking something. 
It could have been worse, but had pumped cooking grease from the prison kitchen. Couldn't avoid it all - a little splashed on my legs. Old french fry odor!
The second event, I avoided the "obstacle" but one of the riders in my group didn't. We are blessed in Idaho with lots of wildlife - highways are deadly to them. We are cruising down a hill on a fairly busy highway, but good shoulders.
I saw the obstacle, there was no traffic, and I avoided it. So did the second rider. The third didn't. The obstacle??? A dead beaver, dead long enough to have a mighty unpleasant odor. A note plugging icon would work well here!
He did some pretty serious scrubbing of his legs at the local watering hole when we took a break!
Hope is a thing with feathers