Girl Scouts have been selling cookies to raise money and learn business skills since 1917. They've sold 100+ flavors over the years, some being more popular than others. According to the organization’s website, the best-selling Girl Scout cookie (RE: most popular) is the Thin Mint.
Thin Mints are so popular you can find the flavor in other products like Dunkin Donuts Thin Mint Iced Coffee and Thin Mint Yoplait yogurt.
Stock up while you can-- cookie season is usually January through April.
Source: Taste of Home; photo: Getty Images