Stormbreaker is a distinct weapon employed by Thor in Avengers: Infinity War and Avengers: Endgame, with the magically-powered axe becoming Thor's main weapon for the two Avengers films, in large part thanks to Groot lending his arm as the hilt.
However, a page from The Road to Marvel's Avengers: Endgame art book reveals how the weapon could have looked if not for Groot's assist.
The art posted to Reddit gives curious fans an idea of what the weapon could have looked like if it had been completed with the typical Asgardian handle, instead of necessitating Groot to help. It's a much sleeker looking weapon as a result, reminiscent of the other weaponry employed by Asgardians, such as Mjolnir. However, the wooden handle of the weapon makes the axe look more distinct, even favoring Jarnbjorn, a weapon used by Thor in the comics.
Stormbreaker was created during Avengers: Infinity War, when Thor, Rocket and Groot traveled to Nidavellir, the cosmic forge. There they encountered Eitri (played by Peter Dinklage), the last of the Drawves, who agreed to try and make a new weapon for Thor. After the blade is crafted, Eitri couldn't find the handle to affix to the weapon, which led to Groot chopping off one of his arms to use as the handle instead.
Directed by Joe and Anthony Russo, Avengers: Endgame stars Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Mark Ruffalo as Bruce Banner, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Brie Larson as Captain Marvel, Paul Rudd as Ant-Man, Don Cheadle as War Machine, Karen Gillan as Nebula, Danai Gurira as Okoye and Bradley Cooper as Rocket, with Gwyneth Paltrow Pepper Potts, Jon Favreau as Happy Hogan, Benedict Wong as Wong, Tessa Thompson as Valkyrie and Josh Brolin as Thanos. The film is in theaters now.