What does this symbol represent from FMA? Who wears it etc..?
All I remember is that its an actual symbol used by RL alchemists during the middle ages
In a strange twist of fate I am going to tell you that this is the symbol belonging to their original alchemy teacher.
To be more specific it is Izumi's Flamel insignia.
The crucified serpent is a symbol used mainly in the creation of the elixir of mercury, and is representative of overcoming or transcending base nature. It is most visibly recognizable as the Staff of Asclepius, the Caduceus of Mercury, the symbol of the modern Doctor's profession.
All right! Thanks for making it clearer.