Fantasy fiction on the big screen tends to follow the traditions and conventions of stories from a thousand years ago. There are always unique spins, but so much of the modern incarnation of the concept takes inspiration from the past. One easy way to innovate is to introduce a new way to resolve conflict, typically in the form of a magical new weapon.
There are a million stories in which a hero must use a magical sword to defeat the villain. In some cases, however, the sword is swapped out for a lance, a bow, a battle ax, or even a gun. The possibilities are endless.
The Black Cauldron
The titular magic item of this film is an ancient relic that holds the power to summon an army of the undead. The Cauldron is the item that drives the plot, it's a terrifyingly powerful armament that doesn't function as any traditional weapon. It's less like a magic wand and more like the battle standard that gives the user the ability to command the army. When the evil Horned King finally gets his hand on the Cauldron, he almost immediately gains incredible power. The typical evil emperor type has an army of minions at their disposal, and this item gives the Horned King that option on a whim. He's only defeated by his physical frailty and the stunning self-sacrifice of one of the heroes. The Black Cauldron is a weapon and an army at once, and its unique capabilities give whoever wields it the power of a god.
Good Samaritan - Hellboy
It's rare to see a good old-fashioned gun on a list of fantasy weapons, but Anung Un Rama's heavy pistol is more than any ordinary firearm. Hellboy is a half-demon who finds himself raised by the founder of a paranormal defense organization. As such, Hellboy is the monster hunter that gets called in to deal with the most troublesome supernatural creatures. He's extremely strong and physically capable, but his weapon of choice is a modified four-round revolver. It's forged from a mix of Irish church bells, cold iron from crucifixes, blessed silver, and a few pieces of the True Cross, making it effectively indestructible. Beyond the weapon, Hellboy creates his own bullets which he's nicknamed Whoppers. Whoppers are explosive rounds that contain an assortment of ingredients that repel monsters, including garlic, white oak, and some more silver. Hellboy's Good Samaritan is the perfect weapon for an urban fantasy monster hunter.
Jadis' Wand - The Chronicles of Narnia
Tons of fantasy villains come to battle with little more than a magical stick and a mastery of the mystic arts. The White Witch Jadis is a capable combatant who wields a few different weapons, most notably her wand. She's an accomplished sword-fighter, and in one of the books she beats up some cops with a lamp post, but her wand is her signature weapon. The film adaptation of the novels added a great visual flair to the weapon, turning it into a beautiful crystal tool. It was capable of casting ice magic and transforming matter, but its go-to move was the ability to turn whoever it touches into stone. Jadis is one of the most enjoyably unpleasant villains in the world of kids' media, so it's no wonder that she turns her wand into a stabbing weapon after it's broken. Jadis' wand is more than a casting implement, it's also one of the most threatening weapons in the world of Narnia.
Epirus Bow - Immortals
Tarsem Singh's 2011 film takes bits and pieces from multiple Greek myths to form a magical new fantasy action story. The driving item of the plot is the mystical Epirus Bow. The film is celebrated for its action setpieces. Almost nothing depicts violence in the way that Immortals does. As the most powerful item in the narrative, the Epirus bow is a marvel to watch. It fires glowing arrows which it seemingly generates from nothing. Those arrows can seemingly fly for miles with unerring accuracy. When they hit their target, they do so with the force of a moving train. They don't pierce their target, they send them flying. The bow is a common fantasy option, but the way this one is presented makes it worthy of the mythology surrounding it.
Kyoketsu-shoge - Ninja Assassin
This minor 2009 martial arts film takes the neo-noir of John Wick and the fantastical depiction of ninjas out of any given anime. Some fantasy weapons are impossible concepts that test the limits of creativity, but this one is ripped from the history books. The Kyoketsu-shoge is a curved dagger on the end of a chain that is attached to a large weight. It's a simple concept, but real ninjas were able to disguise this rope dagger as a simple farming tool. The ninjas of the film, however, can create incredible action setpieces with something as simple as a knife on a chain. It's one of the coolest-looking weapons in modern film, made even more powerful by the fact that it really existed.