Every Character Who Lifted Thor's Hammer Mjolnir
15. Beta Ray Bill
Zeus is a God, so it makes sense that despite his many... shortcomings, as a monarch, he would be able to override the rules of Mjolnir, even if only for a moment. But if you want the first instance of a mortal being just as worthy of Mjolnir as the mighty Thor, you look to Walt Simonson's legendary run on the character, and to Beta Ray Bill!
Although, it might shock you upon first seeing him to know he's worthy, given the monstrous horse face he's got going on.
Yes, an apparent mission statement of Simonson's run on Thor was not only to embrace the weird and wacky with absolutely zero irony, but to use said weird and wackiness to subvert expectations of the reader whenever possible. On any other day, Bill would be just another villain of the week, but under SImonson's masterful writing, he's revealed to be a truly noble hero who is more than worthy of lifting Mjolnir.
Bill even technically wins Mjolnir from Thor in a fair fight when Thor comes to contest Bill's claim to the hammer. But even when he wins, he feels it would be dishonorable to strip Thor of something so dear to him. So Odin compromises by making a new hammer for Bill called Stormbreaker.