One of my favorite low key social engineering hacks is that I used to have a keylogger installed on every machine I own. Whenever a friend needs to hop on my machine to show me something, they'd log into an account they own and I would have their password.
Then I'd do the same Luigi-like low key messing with them for a while. My favorite was when a friend had a VNC server running on their machine with control capabilities. I would sit next to them and subtly jerk the mouse pointer right before they were about to click on something and it drove them mad for a good 20 minutes before I couldn't hold onto the giggles anymore.
edit: To add a bit of context, this was in the Windows 98 era, before the age of social media where we started putting all of our secrets onto our machines. And it was among a group of friends where everyone was trying to hack everyone else and pretty much anything was considered fair game. All of us were high school kids so there wasn't some super serious reputation we had to protect.