Everybody knows about moving Control to Caps Lock. These are my extra neat tricks for my MacBook Pro:

(setq mac-command-modifier 'meta)
(setq mac-option-modifier 'super)
(setq ns-function-modifier 'hyper)

First of all, Meta M- needs to be really easy to hit. On a Mac keyboard, that means Command - and not the default Option - since we want the key that is right next to Space.

The good news is that now Option is available for Super s-. And even more amazing, you can also bind the Function-key to Hyper H- - without losing the ability to change the volume or pause/play.

So now I can use crazy keybindings like H-SPC hyperspace. I haven't entirely decided what I should be using this newfound superpower for, but one thing I've done is reserve all the C-s- prefixed letters for refactorings with js2-refactor, as you can see here.