Bundit's Foot is an Item that can only be found in the form of Golden Pupa loot. When picked up, the player's Luck stat will instantly increase by 50%. This stacks additively with Topiaries and Permanent Upgrades. In short, Luck increases the drop rates of Pickaxes, Rare Seeds, and Fertilizer. It also increases the rate of getting a jackpot at Dicey's Casino. For more info, see Luck Stat.
Bundit's Foot is the best way to increase the Luck stat by a large margin. It causes Enemy drops to improve significantly and will make a visible difference in a run. In addition, it is the only means to increase Luck while the player is actively in a run, giving Bundit's Foot even more value in that regard.