When bringing your computer in for service, here is what you should bring.
Accessories:
Unless you want me to test an accessory, I do not need your accessories. This includes keyboards, mice, monitors, speakers, etc. I have several of all of them in my office.
Laptops:
Bring your laptop and power cord.
Desktop:
If your desktop has a power cord like this, I don’t need it, only bring the tower itself.

If your desktop has a power cord like a laptop (with a transformer in the middle) then please bring it, I may not have a compatible adapter since there are a large variety and the few I have may not be compatible with your computer.