Hacking off the top with the lawnmower or weed whacker. Then when the sprinklers come on, the water shoots 20 ft into the air. It's destroyed and needs replacement after that.
Do you realize that they are supposed to be buried below the height that you mow? They aren't expected to have to mow around sprinkler heads. If there are little short threaded pipes between the heads and pipe in the ground, you can cut them off or buy shorter ones to lower the heads. There are even low profile heads that you can buy that aren't as long as the standard ones so they won't stick up as high.
This is the little pipe screwed into the bottom of the sprinkler head. You can buy short ones or cut them shorter.