I have legitimately used every key on my keyboard, but as someone said, numlock is probably the most useless. Not because I hate its function, but because it should never be turned off. It's caused me more grief by existing and turning itself off than any other single button on the keyboard.
As for being completely functionally useless, I'll go with scroll lock. I've only ever used that outside of KVM switches (I'm sure KVM switches use it only because NO one uses it) back in the days of Loom, where I found it would change the way the scenery would scroll as you moved around the screen. That did NOTHING for gameplay, but it was interesting.
As for being completely functionally useless, I'll go with scroll lock. I've only ever used that outside of KVM switches (I'm sure KVM switches use it only because NO one uses it) back in the days of Loom, where I found it would change the way the scenery would scroll as you moved around the screen. That did NOTHING for gameplay, but it was interesting.