While Thor Odinson has primarily wielded Mjolnir in the comics, there are others who have proven themselves worthy enough to wield the hammer. One of those individuals is Beta Ray Bill, a Korbinite introduced in 1983 who has since gone on to be one of the Marvel Comics universe's most powerful cosmic heroes. While Bill has yet to debut in the Marvel Cinematic Universe, earlier versions of Thor: Ragnarok did include the character, but Marvel Studios president Kevin Feige says that the production ultimately kept Bill out because this kind of appearance wouldn't have done him justice. Feige explained:
There was a Beta Ray Bill, but it was so quick that you would have the same complaints that you have now. He was in it a little bit more and it just didn't do justice. And the feeling is, if you can't do it justice, do it later.
Judging from Kevin Feige's comment to Crave Online, it sounds like the door is still open to introduce Beta Ray Bill in the MCU. When that will happen, that's hard to say. Right now there's no indication that Marvel is interesting in making a fourth Thor movie, but fortunately, Phase Four will expand the cosmic corners of this franchise. So even if the cinematic Beta Ray Bill doesn't pop up in a Thor adventure or even cross paths with the God of Thunder, there will still be other opportunities for him to appear in a more prominent role.
Warning: SPOILERS for Thor: Ragnarok are ahead!
Even though Beta Ray Bill didn't appear in the flesh during Thor: Ragnarok, it appears he was still referenced. If you watched closely during the movie, you noticed that there were some gigantic statues on Sakaar, and one of them seemingly depicted Bill. Presumably this means that Bill was once one of Sakaar's mightiest warriors, and since Marvel is open to introducing the horse-faced alien, that means that he somehow escaped imprisonment and is elsewhere in the galaxy. However, if/when Bill appears, he won't be armed with Mjolnir, as that was destroyed by Hela early into Thor: Ragnarok.
In the comics, Beta Ray Bill briefly obtained Thor's hammer when it was separated from Thor Odinson, but Odin later forged a replacement weapon for Bill called Stormbreaker, which is just as strong as Mjolnir. Bill is also gifted with super strength, speed, agility and durability due to his consciousness being placed in the body of a ferocious, cybernetically-altered, equine-like alien. Outside of the comics, Bill has appeared in the animated TV series Silver Surfer, The Superhero Squad Show and Avengers: Earth's Mightiest Heroes, and he was also featured in the animated movie Planet Hulk.