I usually roam through the middle of the night looking for a base with someone inside cooking or smelting away who’s also near a barred window. While they’re minding their own business, I crouch-walk up to the window as close as I can (usually it’s a few floors up) and then I unload an entire clip of an M4 or MP5 through the window to scare the living b-jebus out of them and then flee. If they’re not near a window and walled in, I just do the same thing but shoot at the wall closest to them… silence and peace suddenly disturbed and they often crap their pants. Did this to a couple of friends on a server before and they were like “WHO’s SHOOTING AT ME???”
“I did… did I scare you?”
Other times when I am feeling creative, I’ll crouch-walk up to the wall they’re on the other side of and plant a C4 onto it and run away and watch it blow from a distance. Scares them even more and they stop everything they’re doing and hide in a corner with whatever weapon they have on them and sit there for 5-10 mins waiting for someone to charge in… then you see them peek outside and look around to see nobody is there.