For example, did you know that this is completely valid C++ code that the GNU C++ compiler (g++) won’t complain about in the slightest:
So yes, a very absurd example, but one that illustrates well how you can use emojis in whatever way you like. 
(Just because you can, does not mean you should.)
Perhaps a better example would be in a Rofi menu, or dmenu. Or inside text files (for example when writing notes and journals). You can even use them in filenames (though why would you in practice, it’s yet unclear, it may make your life a bit more difficult).
Personally, I like to use the 
emoji as my prompt in ZSH.