Recently had to edit the hosts-file on a remote host, and I don't know if using two proxy jumps to SSH into it broke it, but it just wouldn't let me select text with the mouse.
I had to duplicate seven lines and edit the IP addresses, and without being able to copy-paste, I already saw myself manually typing it out.

Then I remembered that in Vim, you can do d5↓ to delete 5 lines. Surely that would also work with copying/yanking. And yep, a y7↓ and a paste later and I had duplicated the lines.

Then use the multi-line cursor like I routinely do for changing all 7 IP addresses...
...and now I feel like I've crossed the line where people will think I'm just a wizard.