It's the built-in WiFi antenna
For my Cerberus build, I'm planning on running ESXi to virtualize my entire PC, hardware passthrough as much as I can, switch between Windows and Linux. The RPi could be used to manage ESXi (to switch VMs, adjust settings, etc.) so I'm going to test it for that purpose. I could also use it for work as a network help if I can make it into something useful with a touch-screen and built-in keyboard.
In the end, I look at my hobbies, interests and projects and I'll always find some use for one.
EDIT: just paired my bluetooth keyboard and mouse I had laying around, now just the HDMI cable and power are attached. I could even let it run for some hours off of my 10.000MAh powerbank, Now all I need is a wireless HDMI transmitter and it could be wireless