in reply to The most useless key on my keyboard is:

I had to vote for the "Windows" key (keys on my keyboard), but not for the reason specified.

I just have never worked out what it (they) are meant to do? They don't appear to do anything in any of the apps I use.

The contextmenu key is useful though.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.