Excalibur

Excalibur is a magic sword that appears in the Season 9 episode "The Smurfs Of The Round Table". It is the legendary sword that was stuck in stone, which a young boy named Arthur had pulled, thus granting him the right to rule over England. It contains magical power that allows its user (normally sorcerers) to cast whatever kind of spells that they wish, though it also produces destructive energy discharges when used as a weapon.

Mainstream Smurfs Media
In the story, King Arthur was wielding Excalibur when his nememis Morgan le Fey stole it from him, using it to turn him and everything in Camelot to wax, to make Sir Lancelot become small, and to turn Merlin into a small rock. She then cast a spell on the sun to burn hotter so that King Arthur and everything she turned to wax would melt away.

The Smurfs who then appeared in Camelot saw what happened and split into two groups, with one group staying behind to keep King Arthur and his men from completely melting, and another group led by Papa Smurf going with Sir Lancelot and Merlin to get Excalibur back from Morgan le Fey. En route to her castle, though, the Smurfs dealt with her Dark Knight, which she sent to stop them. With the help of Merlin's magic wand Sir Will, Papa Smurf cast a spell of magnetism on a giant rock to keep the Dark Knight from going after them, then cast another spell to turn his armor and his little Smurfs' armor to wood.

Seeing that her Dark Knight has failed, Morgan went with Excalibur to stop them herself. Upon the Smurfs' arrival at the castle, she cast a spell that made a giant frying pan appear at their feet, hot enough to fry them. Papa Smurf then cast a spell to make a giant bucket of water appear over them to douse the heat and make the frying pan disappear. Morgan cast her next spell to make a three-headed hellhound appear to attack the Smurfs, which during the attack Merlin ended up rolling down a hill and falling to the bottom of a brook. Papa Smurf countered this by casting a spell to turn a bush into a three-headed hellcat for the hellhound to chase after instead.

Frustrated, Morgan decided to use Excalibur to destroy the Smurfs until the Dark Knight showed up, still pinned to the magnetized giant rock. Excalibur was then wrenched from her hands by the rock, and now that she was without the sword, Papa Smurf turned Morgan into a harmless mouse which the three-headed hellcat chased after. After fishing up Merlin from the rock and removing the spell of magnetism from the rock so that they could control Excalibur, Papa Smurf cast one more spell with Sir Will to make Merlin human again so that he could use Excalibur to restore everything to normal.

With Excalibur back in the hands of its rightful owner, King Arthur commended the Smurfs for their bravery by honoring them with the title "the Smurfs of the Round Table".