You already realized that env vars are an example of dynamic scoping, and someone mentioned exceptions downthread.

But pretty much any serious programming language has some (often crappy ad-hoc) implementation of dynamic scoping somewhere, because it's very useful. Take decimal contexts in python -- would you really like to pass number of significant digits and rounding mode to every operation? Sadly, it's also an example of a crappy ad-hoc implementation (broken with async).