Originally Posted by BMM
In every single X-Men movie he directed. Multiple times.
"He became Magneto."
"...an associate of his called Sabretooth"
"You must be Wolverine."
"I've had Mystique keep you company... she takes so many shapes."
"Toad has a wicked tongue..."
"Call me 'Iceman.'"
"My name is Kurt Wagner, but in the Munich Circus I was called The Incredible Nightcrawler."
Storm is exclusively called Storm
Rogue is exclusively called Rogue
Professor X is called The Professor, unless addressed by Erik.
Magneto is called Magneto, unless addressed by Charles or Raven
Cyclops is called Cyclops, unless addressed by Jean Grey.
And as Zarex points out, goes out of his way to trump that with Magneto's far better and more serious conversation with Pyro.
"What's your name?"
"What's your real name, John?"
I'd say Marvel's track record is pretty similar. Its "Captain" or "Captain Rogers" most often, "Stark" or "Mr. Stark" pretty exclusively. Agent Romanoff, never Black Widow. Agent Barton, unless addressed by Black Widow. And of course, THOR! :P
And villains are worse. Vanko, Stane, Blonsky, Schmidt. I wouldnt say either the Singer or Whedon camp is more likely of using the proper codenames.