5. Captain America Lifts Mjolnir
As some of the first released footage confirmed, a sequence immediately before Ultron appears features the Avengers socialising over some drinks and trying to prove themselves worthy of wielding Mjolnir. Unsurprisingly Tony Stark fails, even with the help of Rhodey and the Iron Man suit, and counter to comic book lore, Captain America also fails, though his worthiness is hinted at by the fact that he is able to move it slightly. That will no doubt annoy fans, since Cap has used the hammer more than once in the comics, but crucially that was always only when Thor was incapable of doing so himself. In many respects, Mjolnir is a personal accessory as much as it a badge of worthiness, and as long as Thor is alive and well, the weapon is linked only to him. Since Thor might not make it to the credits on Earth, there's a very strong suggestion that Cap will once again get the chance to wield the hammer, and this time successfully. That would be the perfect culmination of the arc that shows Stark and Cap in conflict over how best to lead the Avengers.