Thor is one of the most powerful heroes in the Marvel Universe, due in no small part to his impressive hammer, Mjolnir. Only those deemed worthy are capable of even lifting the hammer, so only a handful of heroes besides Thor (such as Beta Ray Bill or Captain America) have ever been able to use the hammer in the core 616-Universe. However, the Marvel multiverse is a large place, with plenty of other versions of Mjolnir that have, in various ways, fallen into the hands of other heroes.
Across the Marvel multiverse, who else besides the Mighty Thor has proven worthy to wield Mjolnir? Here's a breakdown.
Rogue
The X-Men's Rogue was initially a villain, even trading blows with the Avengers in her first appearance. However, as revealed in What If? Vol. 2 #66, her battle with the Avengers led to a much more dramatic conclusion.
Instead of using Thor as a human shield, Rogue absorbs all of the life-energy from the Asgardian and lashes out, unrestrained, with her new abilities to easily bring down the Avengers and kill Vision, Jocasta and Hawkeye. Rogue ends up setting off the Brotherhood into a massive internal fight, leading to the deaths of the whole team besides Rogue, including her adopted mothers Mystique and Destiny. Loki is briefly able to trick Rogue into attacking Asgard in her grief, but Rogue comes to her senses before she can kill Odin. Speaking to Thor's spirit, she embraces the full power of Thor and proves worthy to wield Mjolnir.
Black Widow
What If? Age of Ultron centered around multiple realities, each of which was changed by the sudden demise of one of the Marvel Universe's heroes. In one world, it was Thor who suddenly died while engaged in battle with the Midgard Serpent. Within a month, only a handful of heroes are left fighting against invading Ice Giant armies. Nick Fury, Silver Sable, Black Widow, Microchip, Falcon and Shang-Chi are the last heroes, holed up in Castle Doom.
Deciding to try and bring down the Midgard Serpent or die trying, the group attacks. Black Widow uses the battle as a distraction long enough for her to make her way to Mljonir and lift it. Although most of the heroes die in the battle save for Nick Fury (and Black Widow ends up in another reality), humanity gets the chance to survive thanks to their sacrifice.
Spider-Man 2099
By the time of 2099: Manifest Destiny, the heroes of Marvel's future have already survived multiple near-ends of the world. Heroes like Miguel O'Hara, the Spider-Man of 2099, have even risen into positions of power.
Upon discovering the original Captain America (once again frozen in suspended animation), Miguel and his allies call on Rogers to help save the world from an extinction event that's approaching Earth. Rogers briefly holds Mjolnir while leading his newfound allies, but is a casualty of the mission. In his final moments, he throws Mjolnir to Miguel and tells him to carry on the heroic ideals. This version of the 2099 universe ends with Miguel successfully carrying the hammer -- never taking it into battle, but as a sign of nobility and strength in the boardrooms that controlled the future society.
Silver Surfer
During the events of "Thanos Wins," an ancient version of the Mad Titan is one of the last beings in existence. To wipe out the last of life and force Death to come to him, King Thanos brings the current incarnation of himself to the future to help him. This is because the Fallen, the last being alive, could maybe actually defeat Thanos if he were alone.
The Fallen One is revealed to be the Silver Surfer, now completely black. During their battle, the Surfer reveals he's also spent untold years perfecting himself and his power, making himself worthy to finally call upon Mjolnir and use it as his own. Although the Surfer is worthy to wield it, two Thanos prove too much for the hero to contend with. He ends up mortally wounded, and King Thor kills the Surfer by plunging his head through the handle of the hammer.
Dani Cage
Danielle 'Dani' Cage is the daughter of Luke Cage and Jessica Jones and is gifted with their extraordinary powers. While she's still just a little girl in the current Marvel Universe, she's one of the few remaining heroes alive in the Old Man Logan universe.
When Old Man Logan returns to the world, he tries to help Dani, who's trying to watch over and guide Hulk Jr. to become a better man than his father. After confronting Sabertooth and Mister Sinister, Dani is mortally wounded, but she's able to reach the fallen Mljonir. She takes it up and proves to be worthy enough to use the hammer -- which saves her life by transforming her into Thor. After the final death of Logan, Dani heads off with Hulk Jr. to create a new version of the Avengers and try to salvage the fallen world around them.
Sarah Rogers
Sarah Rogers is one of the teen heroes introduced in What If? Vol. 2 #114. She's one of the children of the Marvel heroes who -- in this reality -- were never able to escape Battle-World after the events of Secret Wars. Sarah is the daughter of Captain America and Rogue, who in this reality ended up having her personality completely overtaken by that of Carol Danvers.
Sarah is born with the powers Rogue absorbed from her mother, giving her super-strength, enhanced endurance and flight. She also proves to be the most natural leader of the group. When the children of the remaining villains try to take power from Doctor Doom, Sarah proves capable of lifting Mjolnir and taking it into battle instead of Thor's son, Bravado. She uses the hammer alongside her father's shield, much like Captain America in Avengers: Endgame.