By popular request (read: more than three poeple asked for it), here's some emojis:    
Couple more:    

Alright alright, here's some more!

Engines   

Tools      

Storefronts    

Last batch for today:     and to show my age,   

"Last batch"? Lies!

More engines:       

More platforms:       

And then,  just because I wanted to add that.

Some more:        

I never realized how unsuitable-for-emojis the Khronos logos are (details too tiny for small sizes, very non-square aspect ratios).

@aras
If we are going smaller in granularity you could give LDtk (https://ldtk.io/) as an Open Source, engine agnostic Level editor an Icon shout out, if you'd like. ^^
It's from the guy who made (among many other things) Dead Cells.
LDtk

LDtk (Level Designer Toolkit) is an open-source 2D level editor for indie devs, with a strong focus on user-friendliness.