This is not a trick nor a hidden capability in Emacs, but it's something I never thought of using until about a mont ago.
In our Emacs configuration, we can define keybindings either global (for use everywhere) or local (for use inside the current buffer) and we do it using
global-set-key. I've mentioned this multiple times in this blog.
Here's an example of how you'd use it
(global-set-key (kbd "H-s") 'save-buffer)
But I recently came to the realization that
global-set-key is an interactive function, which means that you can invoke it as any command in Emacs, via
M-x (or similar).
So I went meta and assigned
k for key or keybinding).
(global-set-key (kbd "H-k") 'global-set-key)
Now if I find myself calling a command regularly or if I want to try a particular keybinding, I just need to hit
H-k, press the desired keys and insert the command name and I'm all set to go.