The Avengers #1 (Marvel, 1963)

he Marvel Era of Super-Heroes started coming together right here! Previously these were all characters in their own books/stories, and although set in the same Universe, they rarely interacted. This origin story for the Avengers tied all of their fates together in a nice big bow.
Here, Iron Man and the Hulk square off before Thor reveals that Loki is the real villain of this first true "team" book in the Marvel Super-Hero universe!