A few of my favorites:
This happens just about everywhere there is a high enough concentration of runners. Though the venerable local mainstay, the Boulder Creek Path, happens to be paved with concrete, for more than 60% of its length there is a well-worn dirt path running parallel alongside it.
The snot rocket. A handy skill that occupies a prominent spot on the toolbelt of any runner who has spent enough time out putting in the miles. Beware of misfires and scatterbombs. Also known as a "farmer blow" by daintier types. The answer to the newbie query, "where do you carry tissues when running?"
Ah, the balance between the necessity to relieve oneself in public and the fear of being discovered doing so, especially where there is scant cover.
No comment here, just throwing this one in for the ladies.