As a daily Emacs user, I find the key-chord package [0] very useful. For example, to save a buffer all I have to press is "hu" (at the same time). It's a simple thing, but saves a little time and lessens "emacs pinky"; I use it hundreds of times a day.
[0] - https://www.emacswiki.org/emacs/KeyChord
In my .emacs.d - https://github.com/celwell/.emacs.d/blob/master/init.el#L261...