This is a bit of a niche post but I recently found I had accidentally started a bunch of duplicate timers all running the same function. I hadn’t recorded the timer objects for them so couldn’t use cancel-timer to kill them. After a bit of searching I discovered the function cancel-function-timers which will cancel all timers that call a particular function.
Not something you’ll be using every day, but might be useful one day!
Pragmatic Emacs 