Great post, @Bastien_Siebman! Here are some additions:
Progress:
Get creative with the use of just these two emoji: 
:
Multi-purpose sets:
Some commonly-used groupings:
Status - Comprehensive:
Emoji help convey the meanings of this single custom field that combines both status and progress:
The first two values (Deferred, Not Started) are for before the task/project begins.
The last two values (Achieved, Failed) are for after it’s done.
The four middle values (Off Track, At Risk, On Track, Ahead) are for when it’s in process.
The color codings are carefully done to communicate info: Green = good; Blue = neutral; Red = bad.
Misc.
I keep these practical emoji for work in a single Asana reference task for jarring my memory or helping get creative, and then do a quick copy/paste to use:
Not all translate here to the Community Forum’s editor, and the last row may not work in Asana in all platforms/browsers I think, but here they are directly in this Forum:
*⃣ #⃣ 0⃣ 1⃣ 2⃣ 3⃣ 4⃣ 5⃣ 6⃣ 7⃣ 8⃣ 9⃣ 
Larry