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

It used to be capslock, but my debian system's XF86Config file now includes the following line:
Option "XkbOptions" "ctrl:nocaps" #disable capslock - +> make ctrl

Also, I DO use the windows key for my window manager (Ion3), and for some reason the "other" windows key (the "menu" key) works for selecting drop-down menus but it's probably the only key I never use.