Fortnite brought a ton of innovations to the battle royale genre, with one of the most notable being the popularization of the Battle Pass system. The Battle Pass serves as a way for players to earn rewards by playing the game, with each new season's pass bringing unique cosmetics and characters. However, Battle Passes weren't introduced until Fortnite's second season. Before Battle Passes and crossover characters, Fortnite's first season of content could be bought with in-game currency at the Season Shop.
The switch between the Season Shop and the Battle Pass is generally seen to be a great move for Fortnite's longevity, though it did have some unforeseen downsides. Certain in-game cosmetics would only ever be offered through the Season Shop and would not return in later Battle Passes. One such cosmetic that comes from Fortnite's first season is the Raider's Revenge pickaxe, which is by far the game's rarest harvesting tool.
While the change from the Season Shop to Battle Passes is a huge reason why Raider's Revenge is so rare, a few other factors go into its exclusivity. For one, players had to be level 35 during Season 1 even to have the chance to buy the epic pickaxe. Once players hit level 35, they still needed to pay the 1500 V-Bucks to buy Raider's Revenge from the Season Shop. That price is generally considered to be the absolute maximum for any harvesting tool with epic tier rarity.
It took a lot of time, money and effort even to have the opportunity to buy Raider's Revenge from the Season Shop. Players didn't have a ton of time to work towards Raider's Revenge either, despite it being one of four items offered in the Season Shop, with none of them being the crossover cosmetics fans are used to today. Fortnite's first season was also its shortest, starting in late October of 2017 and ending in early December. Players only had 50 days to hit level 35 before Raider's Revenge was gone for good.
The only cosmetic that rivals Raider's Revenge is likely the Aeriel Assault Trooper skin, the only character skin from Season 1 not to get some kind of recolor or re-release. However, Aeriel Assault Trooper was only locked behind level 15, making it far more obtainable than Raider's Revenge. The fact that the pickaxe hasn't been re-released and that it was so hard to obtain are likely the two biggest reasons why it's so rare.
Of course, the transition from the Season Shop to Battle Passes is also worth looking at. Each season's Free Pass incentivizes players by giving them cosmetics for simply leveling up, while the 950 V-Buck Battle Passes are available for those who want higher-quality cosmetics. Players aren't grinding levels to individually buy items as they unlock them, instead just leveling up to get cosmetics or paying a cheaper fee for higher-quality unlocks.
It's worth mentioning why Battle Passes are a better system since it highlights why Season 1 items like Raider's Revenge became so rare. They weren't accessible enough to players, with the four Season 1 cosmetics being far more expensive than a single Battle Pass. With many Battle Pass items cycling their way into the in-game store, items from Fortnite Season 2 and onward are often far easier to find than the limited set from Season 1.