[scribu]

I'm a Vim user, so Caps Lock is already assigned to Escape. :)

[asamarin]

I use xcape [1] to have the best of both worlds: a quick press-release tap means Escape (great for vim), while holding it down makes it act as Ctrl (great for shell and other stuff). It's wonderful :)

[1] https://github.com/alols/xcape

[a-b]

You might like to try to map a Ctrl key to the Capslock and use Ctrl + [ as ESC.