From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Z Sword (ゼット ソード, Zetto Sōdo; FUNimation "Z-Sword") is a very ancient and extremely heavy sword which was stuck in a tall mountain on Planet Kaishin. It looks like a European Bastard Sword, also known as a Hand-and-a-Half Sword.
Try as they might, none of the Kaios who attempted it could release the Z Sword. East Kaioshin brought Son Gohan to try and release the sword. Gohan first tried to pull the sword out in his base form. While struggling to get it out, he transformed into a Super Saiyan and with difficulty pulled it free, stunning Kibit, who did not believe that Gohan could pull through.
Gohan had a hard time actually holding the sword, but after many tries, mastering the sword in order to get stronger, became Gohan's primary training. When Son Goku appeared in the planet, he suggested to put the sword into try to see what Gohan could do with the sword, Gohan succeded in slicing some rocks that Goku threw at him, but when Easth Kaioshin threw Gohan a Kachin to see whether he can slice it into two, like the rocks, the Kachin broke the sword into to two, which lead to the Old Kaioshin release.
One of the mini-games that appear while the game is loading in Dragon Ball Z: Budokai Tenkaichi 3 involves Gohan pulling out as many Z Swords as he can.
Gohan can be seen wielding the Z Sword in the background of Training mode in Dragon Ball Z: Tenkaichi Tag Team.
Son Gohan and East Kaioshin go to the Sacred World of the Kais in Dragon Ball Z: Shin Budokai: Another Road to release the Z Sword only to find that Gohan cannot remove it, resulting in their need of the "chosen one". The "chosen one" turns out to be Future Son Gohan, who then proceeds to remove the sword easily. The sword can be seen in the game as a projectile attack used by both Gohan and Future Gohan while using Elder Kai's Unlock Ability.
- The tale of the Z Sword mirrors that of the Arthurian legend of "The Sword in the Stone".