The Dragon Ball franchise doesn't have many notable weapons, with the overwhelming power and capability of the heroes and villains often far outclassing any potential for traditional weapons. While some are relatively new and bizarre additions like the Key Sword, there are some that are intrinsically connected to major characters, such as Trunks' sword and Goku's signature Power Pole, which he was even introduced with.
With that in mind, let's look at the history of Goku's Power Pole and why the weapon stopped being used so much as the Dragon Ball franchise progressed.
The Power Pole was introduced alongside Goku in the very first episode of Dragon Ball. A gift from his adopted father, the Martial Arts Master named Gohan, Goku carries the Power Pole with him throughout his adventures across the world. On top of being an incredibly sturdy magical staff (easily repelling bladed weapons), it also possesses the ability to extend far beyond its initial reach. With some minor concentration, the Power Pole can become longer, giving it a far greater ranger. While fighting Monster Carrot, Goku even used the Power Pole to reach the Moon from the surface of the Earth, leaving the villain and his minions there as punishment for their attacks against Goku and his friends.
The true history of the Power Pole is eventually revealed to be connected to Korin. The ancient Master and grower of the Senzu Beans, the weapon actually once belonged to Korin and was used to connect the top of his tower to the base of the floating Lookout -- home to Kami, the Guardian of Earth. By placing the Power Pole at the very top of his tower, Korin could then extend the staff all the way up to the Lookout, allowing him to climb up and meet Kami. Korin had given it to Master Roshi years earlier when his own adventures had taken him to his Tower, and at some point, Roshi gave it over to his friend Gohan, who passed it down to Goku.
The Power Pole was a frequent tool of Goku's during the events of Dragon Ball, with the young hero using it in battle against the likes of King Piccolo, the Red Ribbon Army and Garlic Jr. However, as the power levels of the heroes increased across Dragon Ball Z, the Power Pole (along with most weapons) were simply outclassed in terms of effectiveness. The weapon was seen sporadically throughout the rest of Dragon Ball Z, typically connecting Korin's Tower with the Lookout -- except for during the anime-only "Garlic Jr. Saga," when Korin bets it during a game of cards. Even its practical use -- giving heroes access to the Lookout -- was rendered moot by the heroes gaining the ability to fly.
Despite this, the Power Pole remains one of the most iconic pieces of gear from the Dragon Ball franchise. Goku has carried it with him in various other media, including many video games. In Dragon Ball Xenoverse, the Power Pole can even be utilized as one of the attacks available to the player character. The DLC- GT Goku character from Dragon Ball FighterZ also utilizes the weapon to great use. Notably, Goku has the Power Pole with him in the final moments of non-canon Dragon Ball GT, which were initially set up as the ultimate conclusion of the Dragon Ball saga. Even in his final form, it's important that Goku still have the Power Pole with him -- one last physical connection between him and the man that raised him.