shieldagent001

Supreme Headquarters, International Espionage, Law-Enforcement Division. (original  name)
or 
Strategic Hazard Intervention, Espionage Logistics Directorate (comices and video games after 1991)
or 
Strategic Homeland Intervention, Enforcement, and Logistics Division (from Marvel movies)

But just call us S.H.I.E.L.D

S.H.I.E.L.D is an internation peacekeeping agency to keep the world safe from any evil force no matter what the cost, and the most deadly and evil threat HYDRA a deep Nazi science under the comand of Colonel Johann Shmidt of the Gestapo aka the RED SKULL