The Kokiri Sword is the first sword that Young Link gets in The Legend of Zelda: Ocarina of Time. He obtains it at the end of a simple maze in Kokiri Village, at the very beginning of the game. It's sharp, capable of killing things, and almost a dagger. Eventually, it is replaced by the legendary blade, the Master Sword. Compared to the Master Sword, the Kokiri Sword is weaker with a much shorter reach.
It makes a re-appearance in Super Smash Bros. Melee. Here, the Kokiri Sword is also defined by its painfully short reach, and its ability to draw in an enemy and do multiple hits in a Great Spin Attack. In The Legend of Zelda: Majora's Mask, this basic sword is eventually replaced by the Gilded Sword, and then the Great Fairy's Sword.