I never use Caps Lock, so I disable the Caps Lock key completely with xmodmap, to avoid hitting it by accident.
Occasionally my X server gets into caps-lock state anyway. (Usually some complicated stunt was involved, like attaching x11vnc to the display remotely.) And then I can't turn it off again using the Caps Lock key.
So I wrote a tiny X client that lets me type 'xcapslock off' at a shell prompt …
… and then I had to make an alias to it, called 'XCAPSLOCK OFF'.
@simontatham Caps Lock becomes Escape for me on any machine I spend any time on.
@alexanderdyas since my previous view of Caps Lock was 'that key I used to keep hitting by accident', I never quite felt it would be a good idea to remap it to any actual action, even a more useful one :-)
@simontatham @alexanderdyas it makes using vim great to have caps lock mapped to escape.