I came across this tip on reddit the other day. It’s probably not something you’ll use every day but it can come in handy when you have a lot of processes in your list-processes output and want to kill a bunch of them. This most often comes up for me when I’m having trouble pushing Git updates and end up with several hung Git processes. Mutiple-cursors is a handy way of getting rid of all of them without worrying about stepping down the list and repeatedly typing d.
It’s not going to revolutionize your workflow but, as I say, it can be a handy time saver occasionally.