The Logitech 250 Deluxe, PS/2 port edition

This absolute definition of the word "durable" has lasted daily use since 2008, it shows no signs of stopping any time soon. I think I'll even start seeking out another NiB one to keep stashed away when this one does finally kick the bucket in another 15+ years. With the hinges/feet up in the back, this is the only keyboard I've used that I can be consistent with both typing WPM or WASD effectiveness without strain on my hands for long hours.

Truly the KOAT for me.