External hard drive big enough to hold more than the entire memory of the computer. Keep everything you find valuable at least, or better yet back up the entire computer on there and update it regularly. Leave it unplugged from the computer between updates.
In other words, an offline backup of everything on your main computer.
A mouse. Just any mouse. There are so many trackpad warriors out there (primarily Apple users) that complain they're being handicapped but they don't just go for the easy solution.
I've even seen some idiots stubbornly trying to do CAD work with a trackpad, and struggling in the process.
Get a fucking mouse.
Monitor arms and/or a standing desk. Monitor arms free up so much space on your desk and having a standing desk is just good for physical health especially if you work from home.
if you draw or photoshop, a wacom screen is a life changer. not an ipad pro or surface, a 20"+ wacom cintiq on a solid desk is still light years beyond anything else out there. also, if you edit video, a usb shuttle wheel with mapable hot buttons makes cutting much faster than click and drag. really good speakers are important. lastly, get the best chair (with a headrest!) you can afford.
One of these, the world's most sophisticated form of protection.
If you are a pc enthusiast I'm going to say you need a sensor panel. I built one myself, 7" lcd display and driver board costs less then 30€ and the result is incredible. I always look at it for any sort of reason it has temperatures, FPS, cpu/gpu/ram usage, network bandwidth.. I always know what's going on!
Refrigerator
Anything you interact with on a daily basis. Keyboard, mouse, desk, monitor... If you're going to be spending a couple hours a day at it why not treat yourself?
Large desk mat comfy chair good keyboard wrist rest decent 1440 monitor
A deej mixer
