Yo-yo: The Weapon of Champions.
In all seriousness, though, this is a fantastically fun game. At times easy, at other times very difficult (especially if you come in from a saved game, meaning you start that area sans items and with only a small amount of life left), and featuring a cast of solid characters (the dialog, for its time, is brilliant!), and including a unique group of items that can be used as weapons (baseballs, baseball bats, the famous yo-yo). The controls could be a little jerky and hard to control (the game is basically laid out on a grid), but that only provides a minor inconvenience for the first few minutes while you try and get used to it. Another revolution that it included was the use of an outside document (that came with the game) as a necessary item to be used in the game: A piece of paper that must be soaked in water so that the secret code would appear. Although it was annoying if you didn't have the paper, for it made it nigh impossible to proceed more than halfway through the game, was an ingenious move to try and bring the game more to life, to include the gamer as an integral part of the game. I cannot think of another game that has used this technique, and I doubt that it ever will be used again.
I can't recommend this game enough to anyone with an NES. You won't know how awesome Star Tropics is until you've played it. Absolutely amazing.