For me, my high bar that I have yet to beat, was the time I pivoted the running OS (ubuntu) into RAM over SSH so I could unmount and image the boot drive without rebooting and loading a live USB (Which would have required a ticket with my provider to enable IPMI)
Migrated a server to a new drive by copying all the files with rsync and chrooting into it. Nothing too impressive from a linux standpoint, but I had no idea that was possible until I tried it.