Say we have two different arrays:

  brands = ["Nike", "Adidas", "Under Armour", "Puma"]
  products = [["shoes", "shirts"],
              ["shoes", "caps", "cleats"],
              ["compressions", "training bands"],
              ["bags", "shoes"]]

and we want something like:

  {
    "Nike"=>["shoes", "shirts"],
    "Adidas"=>["shoes", "caps", "cleats"],
    "Under Armour"=>["compressions", "training bands"],
    "Puma"=>["bags", "shoes"]
  }

This can be achieved easily with this line of code:

  Hash[brands.zip(products)]

This has been useful to me in many scenarios than I can imagine.