In the recently-released teaser for Marvel's Avengers: Age of Ultron, the male members of the team take turns attempting to lift Thor's hammer -- which of course features an inscription to the effect that one must be "worthy" to lift it.
An aside: There has, in fact, been some speculation that Thor will be found unworthy at some point in the film, and go through at least part of the story without the hammer. A number of moments in the trailer appear to show him without it, and there is a similar story currently ongoing in the comics. Furthermore, Civil War, the story on which the third Captain America movie will be based, had no role for Thor, who was either off-world or dead at the time.
At any rate, Scarlett Johansson's Black Widow declines to attempt lifting the hammer, telling her teammates, "That's not a question I need answered."
Hitfix notes that, in fact, there's a precedent for Natasha Romanoff being able to lift the hammer...in an Age of Ultron tale.
Okay, so it was a "What If...?" story. But still.
You can see the pages below, from What If: Age of Ultron #3
Could the decision not to give Natasha a chance to grab at the hammer have been a kind of knowing wink to the readers: "...because we all know she'd lift it right up and make Tony look like a schmuck!"?
Well, probably not. But it's a fun theory, and likely will drive a lot of people to re-read the comic it came from.