What uncommon computer accessories do you find useful? [closed]

This feels like it may not be uncommon, but I have an audio splitter so I can keep my speakers and a set of headphones/mic plugged in at the same time. I can just switch between the two without having to get at the back of my machine.

"External Enclosure
These let you take an internal hard drive and use it as an external one, with a power switch and USB connector. I found one that accepts SATA and PATA drives, and it helped me a lot with migrating files from one computer to another (with different internal drive connector types). Now my old drive serves as an external backup.
I'm not sure how unusual this is, but it was news to me."

Space Mouse. It looks like a hockey puck, but it is a 6 DOF force sensor that lets me move around and rotate 3D drawings. Most 3D CAD programs support them.

"I have an ATEN KVMP switch (similar to this) so that I can switch the keyboard, screen and mouse to one of the physical computers whilst being able to move the headphone connection to the same or a different one.
I, too, have USB extension leads from computers that are not on my desktop to provide Type A, Type B and micro USB connectors on the desktop.
The headphone lead from the ATEN KVM is an extension lead so that I can easily plug in either the headphones or a lead going to an appropriate input socket on an amplifier to allow easy switching to good speakers rather than headphones when appropriate.
A final odd accessory. As I use a USB keyboard and mouse but the BIOS on my main desktop machine does not recognise USB (yes, it is that old), I have a Fujitsu Siemens numeric keypad plugged directly into its keyboard PS2 socket to select boot up options, when needed. Even though my keyboard doesn't have a numeric pad I don't use the numeric keypad for its intended use."

"Bluetack to stop the keyboard moving around.

Duct tape to hold mouse cable where it goes over the back of the desk so the cable weight doesn't drag when you move the mouse.

Screen cleaner (actaully window cleaner) spray.

Paper towels for spilled coffee."